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  97.     <ul>

  98. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code> — Parser for command line options</a><ul>

  99. <li><a class="reference internal" href="#background">Background</a><ul>

  100. <li><a class="reference internal" href="#terminology">Terminology</a></li>

  101. <li><a class="reference internal" href="#what-are-options-for">What are options for?</a></li>

  102. <li><a class="reference internal" href="#what-are-positional-arguments-for">What are positional arguments for?</a></li>

  103. </ul>

  104. </li>

  105. <li><a class="reference internal" href="#tutorial">Tutorial</a><ul>

  106. <li><a class="reference internal" href="#understanding-option-actions">Understanding option actions</a></li>

  107. <li><a class="reference internal" href="#the-store-action">The store action</a></li>

  108. <li><a class="reference internal" href="#handling-boolean-flag-options">Handling boolean (flag) options</a></li>

  109. <li><a class="reference internal" href="#other-actions">Other actions</a></li>

  110. <li><a class="reference internal" href="#default-values">Default values</a></li>

  111. <li><a class="reference internal" href="#generating-help">Generating help</a><ul>

  112. <li><a class="reference internal" href="#grouping-options">Grouping Options</a></li>

  113. </ul>

  114. </li>

  115. <li><a class="reference internal" href="#printing-a-version-string">Printing a version string</a></li>

  116. <li><a class="reference internal" href="#how-optparse-handles-errors">How <code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code> handles errors</a></li>

  117. <li><a class="reference internal" href="#putting-it-all-together">Putting it all together</a></li>

  118. </ul>

  119. </li>

  120. <li><a class="reference internal" href="#reference-guide">Reference Guide</a><ul>

  121. <li><a class="reference internal" href="#creating-the-parser">Creating the parser</a></li>

  122. <li><a class="reference internal" href="#populating-the-parser">Populating the parser</a></li>

  123. <li><a class="reference internal" href="#defining-options">Defining options</a></li>

  124. <li><a class="reference internal" href="#option-attributes">Option attributes</a></li>

  125. <li><a class="reference internal" href="#standard-option-actions">Standard option actions</a></li>

  126. <li><a class="reference internal" href="#standard-option-types">Standard option types</a></li>

  127. <li><a class="reference internal" href="#parsing-arguments">Parsing arguments</a></li>

  128. <li><a class="reference internal" href="#querying-and-manipulating-your-option-parser">Querying and manipulating your option parser</a></li>

  129. <li><a class="reference internal" href="#conflicts-between-options">Conflicts between options</a></li>

  130. <li><a class="reference internal" href="#cleanup">Cleanup</a></li>

  131. <li><a class="reference internal" href="#other-methods">Other methods</a></li>

  132. </ul>

  133. </li>

  134. <li><a class="reference internal" href="#option-callbacks">Option Callbacks</a><ul>

  135. <li><a class="reference internal" href="#defining-a-callback-option">Defining a callback option</a></li>

  136. <li><a class="reference internal" href="#how-callbacks-are-called">How callbacks are called</a></li>

  137. <li><a class="reference internal" href="#raising-errors-in-a-callback">Raising errors in a callback</a></li>

  138. <li><a class="reference internal" href="#callback-example-1-trivial-callback">Callback example 1: trivial callback</a></li>

  139. <li><a class="reference internal" href="#callback-example-2-check-option-order">Callback example 2: check option order</a></li>

  140. <li><a class="reference internal" href="#callback-example-3-check-option-order-generalized">Callback example 3: check option order (generalized)</a></li>

  141. <li><a class="reference internal" href="#callback-example-4-check-arbitrary-condition">Callback example 4: check arbitrary condition</a></li>

  142. <li><a class="reference internal" href="#callback-example-5-fixed-arguments">Callback example 5: fixed arguments</a></li>

  143. <li><a class="reference internal" href="#callback-example-6-variable-arguments">Callback example 6: variable arguments</a></li>

  144. </ul>

  145. </li>

  146. <li><a class="reference internal" href="#extending-optparse">Extending <code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a><ul>

  147. <li><a class="reference internal" href="#adding-new-types">Adding new types</a></li>

  148. <li><a class="reference internal" href="#adding-new-actions">Adding new actions</a></li>

  149. </ul>

  150. </li>

  151. <li><a class="reference internal" href="#exceptions">Exceptions</a></li>

  152. </ul>

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  244.   <section id="module-optparse">

  245. <span id="optparse-parser-for-command-line-options"></span><h1><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> — Parser for command line options<a class="headerlink" href="#module-optparse" title="Link to this heading">¶</a></h1>

  246. <p><strong>Source code:</strong> <a class="reference external" href="https://github.com/python/cpython/tree/3.12/Lib/optparse.py">Lib/optparse.py</a></p>

  247. <div class="deprecated">

  248. <p><span class="versionmodified deprecated">Deprecated since version 3.2: </span>The <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> module is deprecated and will not be developed further;

  249. development will continue with the <a class="reference internal" href="argparse.html#module-argparse" title="argparse: Command-line option and argument parsing library."><code class="xref py py-mod docutils literal notranslate"><span class="pre">argparse</span></code></a> module.</p>

  250. </div>

  251. <hr class="docutils" />

  252. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> is a more convenient, flexible, and powerful library for parsing

  253. command-line options than the old <a class="reference internal" href="getopt.html#module-getopt" title="getopt: Portable parser for command line options; support both short and long option names."><code class="xref py py-mod docutils literal notranslate"><span class="pre">getopt</span></code></a> module.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> uses a

  254. more declarative style of command-line parsing: you create an instance of

  255. <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>, populate it with options, and parse the command

  256. line. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> allows users to specify options in the conventional

  257. GNU/POSIX syntax, and additionally generates usage and help messages for you.</p>

  258. <p>Here’s an example of using <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> in a simple script:</p>

  259. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">optparse</span> <span class="kn">import</span> <span class="n">OptionParser</span>

  260. <span class="o">...</span>

  261. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">()</span>

  262. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">,</span>

  263.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;write report to FILE&quot;</span><span class="p">,</span> <span class="n">metavar</span><span class="o">=</span><span class="s2">&quot;FILE&quot;</span><span class="p">)</span>

  264. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="s2">&quot;--quiet&quot;</span><span class="p">,</span>

  265.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span>

  266.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;don&#39;t print status messages to stdout&quot;</span><span class="p">)</span>

  267. 

  268. <span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  269. </pre></div>

  270. </div>

  271. <p>With these few lines of code, users of your script can now do the “usual thing”

  272. on the command-line, for example:</p>

  273. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">--</span><span class="n">file</span><span class="o">=</span><span class="n">outfile</span> <span class="o">-</span><span class="n">q</span>

  274. </pre></div>

  275. </div>

  276. <p>As it parses the command line, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> sets attributes of the

  277. <code class="docutils literal notranslate"><span class="pre">options</span></code> object returned by <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a> based on user-supplied

  278. command-line values.  When <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a> returns from parsing this command

  279. line, <code class="docutils literal notranslate"><span class="pre">options.filename</span></code> will be <code class="docutils literal notranslate"><span class="pre">&quot;outfile&quot;</span></code> and <code class="docutils literal notranslate"><span class="pre">options.verbose</span></code> will be

  280. <code class="docutils literal notranslate"><span class="pre">False</span></code>.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> supports both long and short options, allows short

  281. options to be merged together, and allows options to be associated with their

  282. arguments in a variety of ways.  Thus, the following command lines are all

  283. equivalent to the above example:</p>

  284. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">-</span><span class="n">f</span> <span class="n">outfile</span> <span class="o">--</span><span class="n">quiet</span>

  285. <span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">--</span><span class="n">quiet</span> <span class="o">--</span><span class="n">file</span> <span class="n">outfile</span>

  286. <span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">-</span><span class="n">q</span> <span class="o">-</span><span class="n">foutfile</span>

  287. <span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">-</span><span class="n">qfoutfile</span>

  288. </pre></div>

  289. </div>

  290. <p>Additionally, users can run one of the following</p>

  291. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">-</span><span class="n">h</span>

  292. <span class="o">&lt;</span><span class="n">yourscript</span><span class="o">&gt;</span> <span class="o">--</span><span class="n">help</span>

  293. </pre></div>

  294. </div>

  295. <p>and <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will print out a brief summary of your script’s options:</p>

  296. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>Usage: &lt;yourscript&gt; [options]

  297. 

  298. Options:

  299.   -h, --help            show this help message and exit

  300.   -f FILE, --file=FILE  write report to FILE

  301.   -q, --quiet           don&#39;t print status messages to stdout

  302. </pre></div>

  303. </div>

  304. <p>where the value of <em>yourscript</em> is determined at runtime (normally from

  305. <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code>).</p>

  306. <section id="background">

  307. <span id="optparse-background"></span><h2>Background<a class="headerlink" href="#background" title="Link to this heading">¶</a></h2>

  308. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> was explicitly designed to encourage the creation of programs

  309. with straightforward, conventional command-line interfaces.  To that end, it

  310. supports only the most common command-line syntax and semantics conventionally

  311. used under Unix.  If you are unfamiliar with these conventions, read this

  312. section to acquaint yourself with them.</p>

  313. <section id="terminology">

  314. <span id="optparse-terminology"></span><h3>Terminology<a class="headerlink" href="#terminology" title="Link to this heading">¶</a></h3>

  315. <dl>

  316. <dt>argument</dt><dd><p>a string entered on the command-line, and passed by the shell to <code class="docutils literal notranslate"><span class="pre">execl()</span></code>

  317. or <code class="docutils literal notranslate"><span class="pre">execv()</span></code>.  In Python, arguments are elements of <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>

  318. (<code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> is the name of the program being executed).  Unix shells

  319. also use the term “word”.</p>

  320. <p>It is occasionally desirable to substitute an argument list other than

  321. <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>, so you should read “argument” as “an element of

  322. <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>, or of some other list provided as a substitute for

  323. <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>”.</p>

  324. </dd>

  325. <dt>option</dt><dd><p>an argument used to supply extra information to guide or customize the

  326. execution of a program.  There are many different syntaxes for options; the

  327. traditional Unix syntax is a hyphen (“-”) followed by a single letter,

  328. e.g. <code class="docutils literal notranslate"><span class="pre">-x</span></code> or <code class="docutils literal notranslate"><span class="pre">-F</span></code>.  Also, traditional Unix syntax allows multiple

  329. options to be merged into a single argument, e.g. <code class="docutils literal notranslate"><span class="pre">-x</span> <span class="pre">-F</span></code> is equivalent

  330. to <code class="docutils literal notranslate"><span class="pre">-xF</span></code>.  The GNU project introduced <code class="docutils literal notranslate"><span class="pre">--</span></code> followed by a series of

  331. hyphen-separated words, e.g. <code class="docutils literal notranslate"><span class="pre">--file</span></code> or <code class="docutils literal notranslate"><span class="pre">--dry-run</span></code>.  These are the

  332. only two option syntaxes provided by <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>.</p>

  333. <p>Some other option syntaxes that the world has seen include:</p>

  334. <ul class="simple">

  335. <li><p>a hyphen followed by a few letters, e.g. <code class="docutils literal notranslate"><span class="pre">-pf</span></code> (this is <em>not</em> the same

  336. as multiple options merged into a single argument)</p></li>

  337. <li><p>a hyphen followed by a whole word, e.g. <code class="docutils literal notranslate"><span class="pre">-file</span></code> (this is technically

  338. equivalent to the previous syntax, but they aren’t usually seen in the same

  339. program)</p></li>

  340. <li><p>a plus sign followed by a single letter, or a few letters, or a word, e.g.

  341. <code class="docutils literal notranslate"><span class="pre">+f</span></code>, <code class="docutils literal notranslate"><span class="pre">+rgb</span></code></p></li>

  342. <li><p>a slash followed by a letter, or a few letters, or a word, e.g. <code class="docutils literal notranslate"><span class="pre">/f</span></code>,

  343. <code class="docutils literal notranslate"><span class="pre">/file</span></code></p></li>

  344. </ul>

  345. <p>These option syntaxes are not supported by <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, and they never

  346. will be.  This is deliberate: the first three are non-standard on any

  347. environment, and the last only makes sense if you’re exclusively targeting

  348. Windows or certain legacy platforms (e.g. VMS, MS-DOS).</p>

  349. </dd>

  350. <dt>option argument</dt><dd><p>an argument that follows an option, is closely associated with that option,

  351. and is consumed from the argument list when that option is. With

  352. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, option arguments may either be in a separate argument from

  353. their option:</p>

  354. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>-f foo

  355. --file foo

  356. </pre></div>

  357. </div>

  358. <p>or included in the same argument:</p>

  359. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>-ffoo

  360. --file=foo

  361. </pre></div>

  362. </div>

  363. <p>Typically, a given option either takes an argument or it doesn’t. Lots of

  364. people want an “optional option arguments” feature, meaning that some options

  365. will take an argument if they see it, and won’t if they don’t.  This is

  366. somewhat controversial, because it makes parsing ambiguous: if <code class="docutils literal notranslate"><span class="pre">-a</span></code> takes

  367. an optional argument and <code class="docutils literal notranslate"><span class="pre">-b</span></code> is another option entirely, how do we

  368. interpret <code class="docutils literal notranslate"><span class="pre">-ab</span></code>?  Because of this ambiguity, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> does not

  369. support this feature.</p>

  370. </dd>

  371. <dt>positional argument</dt><dd><p>something leftover in the argument list after options have been parsed, i.e.

  372. after options and their arguments have been parsed and removed from the

  373. argument list.</p>

  374. </dd>

  375. <dt>required option</dt><dd><p>an option that must be supplied on the command-line; note that the phrase

  376. “required option” is self-contradictory in English.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> doesn’t

  377. prevent you from implementing required options, but doesn’t give you much

  378. help at it either.</p>

  379. </dd>

  380. </dl>

  381. <p>For example, consider this hypothetical command-line:</p>

  382. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">prog</span> <span class="o">-</span><span class="n">v</span> <span class="o">--</span><span class="n">report</span> <span class="n">report</span><span class="o">.</span><span class="n">txt</span> <span class="n">foo</span> <span class="n">bar</span>

  383. </pre></div>

  384. </div>

  385. <p><code class="docutils literal notranslate"><span class="pre">-v</span></code> and <code class="docutils literal notranslate"><span class="pre">--report</span></code> are both options.  Assuming that <code class="docutils literal notranslate"><span class="pre">--report</span></code>

  386. takes one argument, <code class="docutils literal notranslate"><span class="pre">report.txt</span></code> is an option argument.  <code class="docutils literal notranslate"><span class="pre">foo</span></code> and

  387. <code class="docutils literal notranslate"><span class="pre">bar</span></code> are positional arguments.</p>

  388. </section>

  389. <section id="what-are-options-for">

  390. <span id="optparse-what-options-for"></span><h3>What are options for?<a class="headerlink" href="#what-are-options-for" title="Link to this heading">¶</a></h3>

  391. <p>Options are used to provide extra information to tune or customize the execution

  392. of a program.  In case it wasn’t clear, options are usually <em>optional</em>.  A

  393. program should be able to run just fine with no options whatsoever.  (Pick a

  394. random program from the Unix or GNU toolsets.  Can it run without any options at

  395. all and still make sense?  The main exceptions are <code class="docutils literal notranslate"><span class="pre">find</span></code>, <code class="docutils literal notranslate"><span class="pre">tar</span></code>, and

  396. <code class="docutils literal notranslate"><span class="pre">dd</span></code>—all of which are mutant oddballs that have been rightly criticized

  397. for their non-standard syntax and confusing interfaces.)</p>

  398. <p>Lots of people want their programs to have “required options”.  Think about it.

  399. If it’s required, then it’s <em>not optional</em>!  If there is a piece of information

  400. that your program absolutely requires in order to run successfully, that’s what

  401. positional arguments are for.</p>

  402. <p>As an example of good command-line interface design, consider the humble <code class="docutils literal notranslate"><span class="pre">cp</span></code>

  403. utility, for copying files.  It doesn’t make much sense to try to copy files

  404. without supplying a destination and at least one source. Hence, <code class="docutils literal notranslate"><span class="pre">cp</span></code> fails if

  405. you run it with no arguments.  However, it has a flexible, useful syntax that

  406. does not require any options at all:</p>

  407. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">cp</span> <span class="n">SOURCE</span> <span class="n">DEST</span>

  408. <span class="n">cp</span> <span class="n">SOURCE</span> <span class="o">...</span> <span class="n">DEST</span><span class="o">-</span><span class="n">DIR</span>

  409. </pre></div>

  410. </div>

  411. <p>You can get pretty far with just that.  Most <code class="docutils literal notranslate"><span class="pre">cp</span></code> implementations provide a

  412. bunch of options to tweak exactly how the files are copied: you can preserve

  413. mode and modification time, avoid following symlinks, ask before clobbering

  414. existing files, etc.  But none of this distracts from the core mission of

  415. <code class="docutils literal notranslate"><span class="pre">cp</span></code>, which is to copy either one file to another, or several files to another

  416. directory.</p>

  417. </section>

  418. <section id="what-are-positional-arguments-for">

  419. <span id="optparse-what-positional-arguments-for"></span><h3>What are positional arguments for?<a class="headerlink" href="#what-are-positional-arguments-for" title="Link to this heading">¶</a></h3>

  420. <p>Positional arguments are for those pieces of information that your program

  421. absolutely, positively requires to run.</p>

  422. <p>A good user interface should have as few absolute requirements as possible.  If

  423. your program requires 17 distinct pieces of information in order to run

  424. successfully, it doesn’t much matter <em>how</em> you get that information from the

  425. user—most people will give up and walk away before they successfully run the

  426. program.  This applies whether the user interface is a command-line, a

  427. configuration file, or a GUI: if you make that many demands on your users, most

  428. of them will simply give up.</p>

  429. <p>In short, try to minimize the amount of information that users are absolutely

  430. required to supply—use sensible defaults whenever possible.  Of course, you

  431. also want to make your programs reasonably flexible.  That’s what options are

  432. for.  Again, it doesn’t matter if they are entries in a config file, widgets in

  433. the “Preferences” dialog of a GUI, or command-line options—the more options

  434. you implement, the more flexible your program is, and the more complicated its

  435. implementation becomes.  Too much flexibility has drawbacks as well, of course;

  436. too many options can overwhelm users and make your code much harder to maintain.</p>

  437. </section>

  438. </section>

  439. <section id="tutorial">

  440. <span id="optparse-tutorial"></span><h2>Tutorial<a class="headerlink" href="#tutorial" title="Link to this heading">¶</a></h2>

  441. <p>While <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> is quite flexible and powerful, it’s also straightforward

  442. to use in most cases.  This section covers the code patterns that are common to

  443. any <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>-based program.</p>

  444. <p>First, you need to import the OptionParser class; then, early in the main

  445. program, create an OptionParser instance:</p>

  446. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">optparse</span> <span class="kn">import</span> <span class="n">OptionParser</span>

  447. <span class="o">...</span>

  448. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">()</span>

  449. </pre></div>

  450. </div>

  451. <p>Then you can start defining options.  The basic syntax is:</p>

  452. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="n">opt_str</span><span class="p">,</span> <span class="o">...</span><span class="p">,</span>

  453.                   <span class="n">attr</span><span class="o">=</span><span class="n">value</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  454. </pre></div>

  455. </div>

  456. <p>Each option has one or more option strings, such as <code class="docutils literal notranslate"><span class="pre">-f</span></code> or <code class="docutils literal notranslate"><span class="pre">--file</span></code>,

  457. and several option attributes that tell <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> what to expect and what

  458. to do when it encounters that option on the command line.</p>

  459. <p>Typically, each option will have one short option string and one long option

  460. string, e.g.:</p>

  461. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  462. </pre></div>

  463. </div>

  464. <p>You’re free to define as many short option strings and as many long option

  465. strings as you like (including zero), as long as there is at least one option

  466. string overall.</p>

  467. <p>The option strings passed to <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a> are effectively

  468. labels for the

  469. option defined by that call.  For brevity, we will frequently refer to

  470. <em>encountering an option</em> on the command line; in reality, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  471. encounters <em>option strings</em> and looks up options from them.</p>

  472. <p>Once all of your options are defined, instruct <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to parse your

  473. program’s command line:</p>

  474. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  475. </pre></div>

  476. </div>

  477. <p>(If you like, you can pass a custom argument list to <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a>, but

  478. that’s rarely necessary: by default it uses <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>.)</p>

  479. <p><a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a> returns two values:</p>

  480. <ul class="simple">

  481. <li><p><code class="docutils literal notranslate"><span class="pre">options</span></code>, an object containing values for all of your options—e.g. if

  482. <code class="docutils literal notranslate"><span class="pre">--file</span></code> takes a single string argument, then <code class="docutils literal notranslate"><span class="pre">options.file</span></code> will be the

  483. filename supplied by the user, or <code class="docutils literal notranslate"><span class="pre">None</span></code> if the user did not supply that

  484. option</p></li>

  485. <li><p><code class="docutils literal notranslate"><span class="pre">args</span></code>, the list of positional arguments leftover after parsing options</p></li>

  486. </ul>

  487. <p>This tutorial section only covers the four most important option attributes:

  488. <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a>, <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>, <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>

  489. (destination), and <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a>. Of these, <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a> is the

  490. most fundamental.</p>

  491. <section id="understanding-option-actions">

  492. <span id="optparse-understanding-option-actions"></span><h3>Understanding option actions<a class="headerlink" href="#understanding-option-actions" title="Link to this heading">¶</a></h3>

  493. <p>Actions tell <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> what to do when it encounters an option on the

  494. command line.  There is a fixed set of actions hard-coded into <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>;

  495. adding new actions is an advanced topic covered in section

  496. <a class="reference internal" href="#optparse-extending-optparse"><span class="std std-ref">Extending optparse</span></a>.  Most actions tell <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to store

  497. a value in some variable—for example, take a string from the command line and

  498. store it in an attribute of <code class="docutils literal notranslate"><span class="pre">options</span></code>.</p>

  499. <p>If you don’t specify an option action, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> defaults to <code class="docutils literal notranslate"><span class="pre">store</span></code>.</p>

  500. </section>

  501. <section id="the-store-action">

  502. <span id="optparse-store-action"></span><h3>The store action<a class="headerlink" href="#the-store-action" title="Link to this heading">¶</a></h3>

  503. <p>The most common option action is <code class="docutils literal notranslate"><span class="pre">store</span></code>, which tells <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to take

  504. the next argument (or the remainder of the current argument), ensure that it is

  505. of the correct type, and store it to your chosen destination.</p>

  506. <p>For example:</p>

  507. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span>

  508.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;string&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">)</span>

  509. </pre></div>

  510. </div>

  511. <p>Now let’s make up a fake command line and ask <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to parse it:</p>

  512. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">args</span> <span class="o">=</span> <span class="p">[</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;foo.txt&quot;</span><span class="p">]</span>

  513. <span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">(</span><span class="n">args</span><span class="p">)</span>

  514. </pre></div>

  515. </div>

  516. <p>When <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> sees the option string <code class="docutils literal notranslate"><span class="pre">-f</span></code>, it consumes the next

  517. argument, <code class="docutils literal notranslate"><span class="pre">foo.txt</span></code>, and stores it in <code class="docutils literal notranslate"><span class="pre">options.filename</span></code>.  So, after this

  518. call to <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a>, <code class="docutils literal notranslate"><span class="pre">options.filename</span></code> is <code class="docutils literal notranslate"><span class="pre">&quot;foo.txt&quot;</span></code>.</p>

  519. <p>Some other option types supported by <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> are <code class="docutils literal notranslate"><span class="pre">int</span></code> and <code class="docutils literal notranslate"><span class="pre">float</span></code>.

  520. Here’s an option that expects an integer argument:</p>

  521. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-n&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;int&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;num&quot;</span><span class="p">)</span>

  522. </pre></div>

  523. </div>

  524. <p>Note that this option has no long option string, which is perfectly acceptable.

  525. Also, there’s no explicit action, since the default is <code class="docutils literal notranslate"><span class="pre">store</span></code>.</p>

  526. <p>Let’s parse another fake command-line.  This time, we’ll jam the option argument

  527. right up against the option: since <code class="docutils literal notranslate"><span class="pre">-n42</span></code> (one argument) is equivalent to

  528. <code class="docutils literal notranslate"><span class="pre">-n</span> <span class="pre">42</span></code> (two arguments), the code</p>

  529. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">([</span><span class="s2">&quot;-n42&quot;</span><span class="p">])</span>

  530. <span class="nb">print</span><span class="p">(</span><span class="n">options</span><span class="o">.</span><span class="n">num</span><span class="p">)</span>

  531. </pre></div>

  532. </div>

  533. <p>will print <code class="docutils literal notranslate"><span class="pre">42</span></code>.</p>

  534. <p>If you don’t specify a type, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> assumes <code class="docutils literal notranslate"><span class="pre">string</span></code>.  Combined with

  535. the fact that the default action is <code class="docutils literal notranslate"><span class="pre">store</span></code>, that means our first example can

  536. be a lot shorter:</p>

  537. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">)</span>

  538. </pre></div>

  539. </div>

  540. <p>If you don’t supply a destination, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> figures out a sensible

  541. default from the option strings: if the first long option string is

  542. <code class="docutils literal notranslate"><span class="pre">--foo-bar</span></code>, then the default destination is <code class="docutils literal notranslate"><span class="pre">foo_bar</span></code>.  If there are no

  543. long option strings, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> looks at the first short option string: the

  544. default destination for <code class="docutils literal notranslate"><span class="pre">-f</span></code> is <code class="docutils literal notranslate"><span class="pre">f</span></code>.</p>

  545. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> also includes the built-in <code class="docutils literal notranslate"><span class="pre">complex</span></code> type.  Adding

  546. types is covered in section <a class="reference internal" href="#optparse-extending-optparse"><span class="std std-ref">Extending optparse</span></a>.</p>

  547. </section>

  548. <section id="handling-boolean-flag-options">

  549. <span id="optparse-handling-boolean-options"></span><h3>Handling boolean (flag) options<a class="headerlink" href="#handling-boolean-flag-options" title="Link to this heading">¶</a></h3>

  550. <p>Flag options—set a variable to true or false when a particular option is

  551. seen—are quite common.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> supports them with two separate actions,

  552. <code class="docutils literal notranslate"><span class="pre">store_true</span></code> and <code class="docutils literal notranslate"><span class="pre">store_false</span></code>.  For example, you might have a <code class="docutils literal notranslate"><span class="pre">verbose</span></code>

  553. flag that is turned on with <code class="docutils literal notranslate"><span class="pre">-v</span></code> and off with <code class="docutils literal notranslate"><span class="pre">-q</span></code>:</p>

  554. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  555. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  556. </pre></div>

  557. </div>

  558. <p>Here we have two different options with the same destination, which is perfectly

  559. OK.  (It just means you have to be a bit careful when setting default

  560. values—see below.)</p>

  561. <p>When <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> encounters <code class="docutils literal notranslate"><span class="pre">-v</span></code> on the command line, it sets

  562. <code class="docutils literal notranslate"><span class="pre">options.verbose</span></code> to <code class="docutils literal notranslate"><span class="pre">True</span></code>; when it encounters <code class="docutils literal notranslate"><span class="pre">-q</span></code>,

  563. <code class="docutils literal notranslate"><span class="pre">options.verbose</span></code> is set to <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>

  564. </section>

  565. <section id="other-actions">

  566. <span id="optparse-other-actions"></span><h3>Other actions<a class="headerlink" href="#other-actions" title="Link to this heading">¶</a></h3>

  567. <p>Some other actions supported by <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> are:</p>

  568. <dl class="simple">

  569. <dt><code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code></dt><dd><p>store a constant value, pre-set via <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Option.const</span></code></a></p>

  570. </dd>

  571. <dt><code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code></dt><dd><p>append this option’s argument to a list</p>

  572. </dd>

  573. <dt><code class="docutils literal notranslate"><span class="pre">&quot;count&quot;</span></code></dt><dd><p>increment a counter by one</p>

  574. </dd>

  575. <dt><code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code></dt><dd><p>call a specified function</p>

  576. </dd>

  577. </dl>

  578. <p>These are covered in section <a class="reference internal" href="#optparse-reference-guide"><span class="std std-ref">Reference Guide</span></a>,

  579. and section <a class="reference internal" href="#optparse-option-callbacks"><span class="std std-ref">Option Callbacks</span></a>.</p>

  580. </section>

  581. <section id="default-values">

  582. <span id="optparse-default-values"></span><h3>Default values<a class="headerlink" href="#default-values" title="Link to this heading">¶</a></h3>

  583. <p>All of the above examples involve setting some variable (the “destination”) when

  584. certain command-line options are seen.  What happens if those options are never

  585. seen?  Since we didn’t supply any defaults, they are all set to <code class="docutils literal notranslate"><span class="pre">None</span></code>.  This

  586. is usually fine, but sometimes you want more control.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> lets you

  587. supply a default value for each destination, which is assigned before the

  588. command line is parsed.</p>

  589. <p>First, consider the verbose/quiet example.  If we want <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to set

  590. <code class="docutils literal notranslate"><span class="pre">verbose</span></code> to <code class="docutils literal notranslate"><span class="pre">True</span></code> unless <code class="docutils literal notranslate"><span class="pre">-q</span></code> is seen, then we can do this:</p>

  591. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  592. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  593. </pre></div>

  594. </div>

  595. <p>Since default values apply to the <em>destination</em> rather than to any particular

  596. option, and these two options happen to have the same destination, this is

  597. exactly equivalent:</p>

  598. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  599. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  600. </pre></div>

  601. </div>

  602. <p>Consider this:</p>

  603. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>

  604. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  605. </pre></div>

  606. </div>

  607. <p>Again, the default value for <code class="docutils literal notranslate"><span class="pre">verbose</span></code> will be <code class="docutils literal notranslate"><span class="pre">True</span></code>: the last default

  608. value supplied for any particular destination is the one that counts.</p>

  609. <p>A clearer way to specify default values is the <code class="xref py py-meth docutils literal notranslate"><span class="pre">set_defaults()</span></code> method of

  610. OptionParser, which you can call at any time before calling

  611. <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a>:</p>

  612. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">set_defaults</span><span class="p">(</span><span class="n">verbose</span><span class="o">=</span><span class="kc">True</span><span class="p">)</span>

  613. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>

  614. <span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  615. </pre></div>

  616. </div>

  617. <p>As before, the last value specified for a given option destination is the one

  618. that counts.  For clarity, try to use one method or the other of setting default

  619. values, not both.</p>

  620. </section>

  621. <section id="generating-help">

  622. <span id="optparse-generating-help"></span><h3>Generating help<a class="headerlink" href="#generating-help" title="Link to this heading">¶</a></h3>

  623. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s ability to generate help and usage text automatically is

  624. useful for creating user-friendly command-line interfaces.  All you have to do

  625. is supply a <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> value for each option, and optionally a short

  626. usage message for your whole program.  Here’s an OptionParser populated with

  627. user-friendly (documented) options:</p>

  628. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">usage</span> <span class="o">=</span> <span class="s2">&quot;usage: %prog [options] arg1 arg2&quot;</span>

  629. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">usage</span><span class="o">=</span><span class="n">usage</span><span class="p">)</span>

  630. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="s2">&quot;--verbose&quot;</span><span class="p">,</span>

  631.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="kc">True</span><span class="p">,</span>

  632.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;make lots of noise [default]&quot;</span><span class="p">)</span>

  633. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="s2">&quot;--quiet&quot;</span><span class="p">,</span>

  634.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span>

  635.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;be vewwy quiet (I&#39;m hunting wabbits)&quot;</span><span class="p">)</span>

  636. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--filename&quot;</span><span class="p">,</span>

  637.                   <span class="n">metavar</span><span class="o">=</span><span class="s2">&quot;FILE&quot;</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;write output to FILE&quot;</span><span class="p">)</span>

  638. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-m&quot;</span><span class="p">,</span> <span class="s2">&quot;--mode&quot;</span><span class="p">,</span>

  639.                   <span class="n">default</span><span class="o">=</span><span class="s2">&quot;intermediate&quot;</span><span class="p">,</span>

  640.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;interaction mode: novice, intermediate, &quot;</span>

  641.                        <span class="s2">&quot;or expert [default: </span><span class="si">%d</span><span class="s2">efault]&quot;</span><span class="p">)</span>

  642. </pre></div>

  643. </div>

  644. <p>If <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> encounters either <code class="docutils literal notranslate"><span class="pre">-h</span></code> or <code class="docutils literal notranslate"><span class="pre">--help</span></code> on the

  645. command-line, or if you just call <code class="xref py py-meth docutils literal notranslate"><span class="pre">parser.print_help()</span></code>, it prints the

  646. following to standard output:</p>

  647. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>Usage: &lt;yourscript&gt; [options] arg1 arg2

  648. 

  649. Options:

  650.   -h, --help            show this help message and exit

  651.   -v, --verbose         make lots of noise [default]

  652.   -q, --quiet           be vewwy quiet (I&#39;m hunting wabbits)

  653.   -f FILE, --filename=FILE

  654.                         write output to FILE

  655.   -m MODE, --mode=MODE  interaction mode: novice, intermediate, or

  656.                         expert [default: intermediate]

  657. </pre></div>

  658. </div>

  659. <p>(If the help output is triggered by a help option, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> exits after

  660. printing the help text.)</p>

  661. <p>There’s a lot going on here to help <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> generate the best possible

  662. help message:</p>

  663. <ul>

  664. <li><p>the script defines its own usage message:</p>

  665. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">usage</span> <span class="o">=</span> <span class="s2">&quot;usage: %prog [options] arg1 arg2&quot;</span>

  666. </pre></div>

  667. </div>

  668. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> expands <code class="docutils literal notranslate"><span class="pre">%prog</span></code> in the usage string to the name of the

  669. current program, i.e. <code class="docutils literal notranslate"><span class="pre">os.path.basename(sys.argv[0])</span></code>.  The expanded string

  670. is then printed before the detailed option help.</p>

  671. <p>If you don’t supply a usage string, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> uses a bland but sensible

  672. default: <code class="docutils literal notranslate"><span class="pre">&quot;Usage:</span> <span class="pre">%prog</span> <span class="pre">[options]&quot;</span></code>, which is fine if your script doesn’t

  673. take any positional arguments.</p>

  674. </li>

  675. <li><p>every option defines a help string, and doesn’t worry about

  676. line-wrapping—<a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> takes care of wrapping lines and making

  677. the help output look good.</p></li>

  678. <li><p>options that take a value indicate this fact in their automatically generated

  679. help message, e.g. for the “mode” option:</p>

  680. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-</span><span class="n">m</span> <span class="n">MODE</span><span class="p">,</span> <span class="o">--</span><span class="n">mode</span><span class="o">=</span><span class="n">MODE</span>

  681. </pre></div>

  682. </div>

  683. <p>Here, “MODE” is called the meta-variable: it stands for the argument that the

  684. user is expected to supply to <code class="docutils literal notranslate"><span class="pre">-m</span></code>/<code class="docutils literal notranslate"><span class="pre">--mode</span></code>.  By default,

  685. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> converts the destination variable name to uppercase and uses

  686. that for the meta-variable.  Sometimes, that’s not what you want—for

  687. example, the <code class="docutils literal notranslate"><span class="pre">--filename</span></code> option explicitly sets <code class="docutils literal notranslate"><span class="pre">metavar=&quot;FILE&quot;</span></code>,

  688. resulting in this automatically generated option description:</p>

  689. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-</span><span class="n">f</span> <span class="n">FILE</span><span class="p">,</span> <span class="o">--</span><span class="n">filename</span><span class="o">=</span><span class="n">FILE</span>

  690. </pre></div>

  691. </div>

  692. <p>This is important for more than just saving space, though: the manually

  693. written help text uses the meta-variable <code class="docutils literal notranslate"><span class="pre">FILE</span></code> to clue the user in that

  694. there’s a connection between the semi-formal syntax <code class="docutils literal notranslate"><span class="pre">-f</span> <span class="pre">FILE</span></code> and the informal

  695. semantic description “write output to FILE”. This is a simple but effective

  696. way to make your help text a lot clearer and more useful for end users.</p>

  697. </li>

  698. <li><p>options that have a default value can include <code class="docutils literal notranslate"><span class="pre">%default</span></code> in the help

  699. string—<a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will replace it with <a class="reference internal" href="stdtypes.html#str" title="str"><code class="xref py py-func docutils literal notranslate"><span class="pre">str()</span></code></a> of the option’s

  700. default value.  If an option has no default value (or the default value is

  701. <code class="docutils literal notranslate"><span class="pre">None</span></code>), <code class="docutils literal notranslate"><span class="pre">%default</span></code> expands to <code class="docutils literal notranslate"><span class="pre">none</span></code>.</p></li>

  702. </ul>

  703. <section id="grouping-options">

  704. <h4>Grouping Options<a class="headerlink" href="#grouping-options" title="Link to this heading">¶</a></h4>

  705. <p>When dealing with many options, it is convenient to group these options for

  706. better help output.  An <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a> can contain several option groups,

  707. each of which can contain several options.</p>

  708. <p>An option group is obtained using the class <a class="reference internal" href="#optparse.OptionGroup" title="optparse.OptionGroup"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionGroup</span></code></a>:</p>

  709. <dl class="py class">

  710. <dt class="sig sig-object py" id="optparse.OptionGroup">

  711. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">OptionGroup</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">parser</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">title</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">description</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionGroup" title="Link to this definition">¶</a></dt>

  712. <dd><p>where</p>

  713. <ul class="simple">

  714. <li><p>parser is the <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a> instance the group will be inserted in

  715. to</p></li>

  716. <li><p>title is the group title</p></li>

  717. <li><p>description, optional, is a long description of the group</p></li>

  718. </ul>

  719. </dd></dl>

  720. 

  721. <p><a class="reference internal" href="#optparse.OptionGroup" title="optparse.OptionGroup"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionGroup</span></code></a> inherits from <code class="xref py py-class docutils literal notranslate"><span class="pre">OptionContainer</span></code> (like

  722. <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>) and so the <code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code> method can be used to add

  723. an option to the group.</p>

  724. <p>Once all the options are declared, using the <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a> method

  725. <code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option_group()</span></code> the group is added to the previously defined parser.</p>

  726. <p>Continuing with the parser defined in the previous section, adding an

  727. <a class="reference internal" href="#optparse.OptionGroup" title="optparse.OptionGroup"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionGroup</span></code></a> to a parser is easy:</p>

  728. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">group</span> <span class="o">=</span> <span class="n">OptionGroup</span><span class="p">(</span><span class="n">parser</span><span class="p">,</span> <span class="s2">&quot;Dangerous Options&quot;</span><span class="p">,</span>

  729.                     <span class="s2">&quot;Caution: use these options at your own risk.  &quot;</span>

  730.                     <span class="s2">&quot;It is believed that some of them bite.&quot;</span><span class="p">)</span>

  731. <span class="n">group</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-g&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Group option.&quot;</span><span class="p">)</span>

  732. <span class="n">parser</span><span class="o">.</span><span class="n">add_option_group</span><span class="p">(</span><span class="n">group</span><span class="p">)</span>

  733. </pre></div>

  734. </div>

  735. <p>This would result in the following help output:</p>

  736. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>Usage: &lt;yourscript&gt; [options] arg1 arg2

  737. 

  738. Options:

  739.   -h, --help            show this help message and exit

  740.   -v, --verbose         make lots of noise [default]

  741.   -q, --quiet           be vewwy quiet (I&#39;m hunting wabbits)

  742.   -f FILE, --filename=FILE

  743.                         write output to FILE

  744.   -m MODE, --mode=MODE  interaction mode: novice, intermediate, or

  745.                         expert [default: intermediate]

  746. 

  747.   Dangerous Options:

  748.     Caution: use these options at your own risk.  It is believed that some

  749.     of them bite.

  750. 

  751.     -g                  Group option.

  752. </pre></div>

  753. </div>

  754. <p>A bit more complete example might involve using more than one group: still

  755. extending the previous example:</p>

  756. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">group</span> <span class="o">=</span> <span class="n">OptionGroup</span><span class="p">(</span><span class="n">parser</span><span class="p">,</span> <span class="s2">&quot;Dangerous Options&quot;</span><span class="p">,</span>

  757.                     <span class="s2">&quot;Caution: use these options at your own risk.  &quot;</span>

  758.                     <span class="s2">&quot;It is believed that some of them bite.&quot;</span><span class="p">)</span>

  759. <span class="n">group</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-g&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Group option.&quot;</span><span class="p">)</span>

  760. <span class="n">parser</span><span class="o">.</span><span class="n">add_option_group</span><span class="p">(</span><span class="n">group</span><span class="p">)</span>

  761. 

  762. <span class="n">group</span> <span class="o">=</span> <span class="n">OptionGroup</span><span class="p">(</span><span class="n">parser</span><span class="p">,</span> <span class="s2">&quot;Debug Options&quot;</span><span class="p">)</span>

  763. <span class="n">group</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-d&quot;</span><span class="p">,</span> <span class="s2">&quot;--debug&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span>

  764.                  <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Print debug information&quot;</span><span class="p">)</span>

  765. <span class="n">group</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-s&quot;</span><span class="p">,</span> <span class="s2">&quot;--sql&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span>

  766.                  <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Print all SQL statements executed&quot;</span><span class="p">)</span>

  767. <span class="n">group</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-e&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Print every action done&quot;</span><span class="p">)</span>

  768. <span class="n">parser</span><span class="o">.</span><span class="n">add_option_group</span><span class="p">(</span><span class="n">group</span><span class="p">)</span>

  769. </pre></div>

  770. </div>

  771. <p>that results in the following output:</p>

  772. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>Usage: &lt;yourscript&gt; [options] arg1 arg2

  773. 

  774. Options:

  775.   -h, --help            show this help message and exit

  776.   -v, --verbose         make lots of noise [default]

  777.   -q, --quiet           be vewwy quiet (I&#39;m hunting wabbits)

  778.   -f FILE, --filename=FILE

  779.                         write output to FILE

  780.   -m MODE, --mode=MODE  interaction mode: novice, intermediate, or expert

  781.                         [default: intermediate]

  782. 

  783.   Dangerous Options:

  784.     Caution: use these options at your own risk.  It is believed that some

  785.     of them bite.

  786. 

  787.     -g                  Group option.

  788. 

  789.   Debug Options:

  790.     -d, --debug         Print debug information

  791.     -s, --sql           Print all SQL statements executed

  792.     -e                  Print every action done

  793. </pre></div>

  794. </div>

  795. <p>Another interesting method, in particular when working programmatically with

  796. option groups is:</p>

  797. <dl class="py method">

  798. <dt class="sig sig-object py" id="optparse.OptionParser.get_option_group">

  799. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">get_option_group</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">opt_str</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.get_option_group" title="Link to this definition">¶</a></dt>

  800. <dd><p>Return the <a class="reference internal" href="#optparse.OptionGroup" title="optparse.OptionGroup"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionGroup</span></code></a> to which the short or long option

  801. string <em>opt_str</em> (e.g. <code class="docutils literal notranslate"><span class="pre">'-o'</span></code> or <code class="docutils literal notranslate"><span class="pre">'--option'</span></code>) belongs. If

  802. there’s no such <a class="reference internal" href="#optparse.OptionGroup" title="optparse.OptionGroup"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionGroup</span></code></a>, return <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  803. </dd></dl>

  804. 

  805. </section>

  806. </section>

  807. <section id="printing-a-version-string">

  808. <span id="optparse-printing-version-string"></span><h3>Printing a version string<a class="headerlink" href="#printing-a-version-string" title="Link to this heading">¶</a></h3>

  809. <p>Similar to the brief usage string, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> can also print a version

  810. string for your program.  You have to supply the string as the <code class="docutils literal notranslate"><span class="pre">version</span></code>

  811. argument to OptionParser:</p>

  812. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">usage</span><span class="o">=</span><span class="s2">&quot;%prog [-f] [-q]&quot;</span><span class="p">,</span> <span class="n">version</span><span class="o">=</span><span class="s2">&quot;%prog 1.0&quot;</span><span class="p">)</span>

  813. </pre></div>

  814. </div>

  815. <p><code class="docutils literal notranslate"><span class="pre">%prog</span></code> is expanded just like it is in <code class="docutils literal notranslate"><span class="pre">usage</span></code>.  Apart from that,

  816. <code class="docutils literal notranslate"><span class="pre">version</span></code> can contain anything you like.  When you supply it, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  817. automatically adds a <code class="docutils literal notranslate"><span class="pre">--version</span></code> option to your parser. If it encounters

  818. this option on the command line, it expands your <code class="docutils literal notranslate"><span class="pre">version</span></code> string (by

  819. replacing <code class="docutils literal notranslate"><span class="pre">%prog</span></code>), prints it to stdout, and exits.</p>

  820. <p>For example, if your script is called <code class="docutils literal notranslate"><span class="pre">/usr/bin/foo</span></code>:</p>

  821. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>/usr/bin/foo<span class="w"> </span>--version

  822. <span class="go">foo 1.0</span>

  823. </pre></div>

  824. </div>

  825. <p>The following two methods can be used to print and get the <code class="docutils literal notranslate"><span class="pre">version</span></code> string:</p>

  826. <dl class="py method">

  827. <dt class="sig sig-object py" id="optparse.OptionParser.print_version">

  828. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">print_version</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">file</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.print_version" title="Link to this definition">¶</a></dt>

  829. <dd><p>Print the version message for the current program (<code class="docutils literal notranslate"><span class="pre">self.version</span></code>) to

  830. <em>file</em> (default stdout).  As with <a class="reference internal" href="#optparse.OptionParser.print_usage" title="optparse.OptionParser.print_usage"><code class="xref py py-meth docutils literal notranslate"><span class="pre">print_usage()</span></code></a>, any occurrence

  831. of <code class="docutils literal notranslate"><span class="pre">%prog</span></code> in <code class="docutils literal notranslate"><span class="pre">self.version</span></code> is replaced with the name of the current

  832. program.  Does nothing if <code class="docutils literal notranslate"><span class="pre">self.version</span></code> is empty or undefined.</p>

  833. </dd></dl>

  834. 

  835. <dl class="py method">

  836. <dt class="sig sig-object py" id="optparse.OptionParser.get_version">

  837. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">get_version</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.get_version" title="Link to this definition">¶</a></dt>

  838. <dd><p>Same as <a class="reference internal" href="#optparse.OptionParser.print_version" title="optparse.OptionParser.print_version"><code class="xref py py-meth docutils literal notranslate"><span class="pre">print_version()</span></code></a> but returns the version string instead of

  839. printing it.</p>

  840. </dd></dl>

  841. 

  842. </section>

  843. <section id="how-optparse-handles-errors">

  844. <span id="optparse-how-optparse-handles-errors"></span><h3>How <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> handles errors<a class="headerlink" href="#how-optparse-handles-errors" title="Link to this heading">¶</a></h3>

  845. <p>There are two broad classes of errors that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> has to worry about:

  846. programmer errors and user errors.  Programmer errors are usually erroneous

  847. calls to <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-func docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a>, e.g. invalid option strings, unknown

  848. option attributes, missing option attributes, etc.  These are dealt with in the

  849. usual way: raise an exception (either <a class="reference internal" href="#optparse.OptionError" title="optparse.OptionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">optparse.OptionError</span></code></a> or

  850. <a class="reference internal" href="exceptions.html#TypeError" title="TypeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">TypeError</span></code></a>) and let the program crash.</p>

  851. <p>Handling user errors is much more important, since they are guaranteed to happen

  852. no matter how stable your code is.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> can automatically detect

  853. some user errors, such as bad option arguments (passing <code class="docutils literal notranslate"><span class="pre">-n</span> <span class="pre">4x</span></code> where

  854. <code class="docutils literal notranslate"><span class="pre">-n</span></code> takes an integer argument), missing arguments (<code class="docutils literal notranslate"><span class="pre">-n</span></code> at the end

  855. of the command line, where <code class="docutils literal notranslate"><span class="pre">-n</span></code> takes an argument of any type).  Also,

  856. you can call <code class="xref py py-func docutils literal notranslate"><span class="pre">OptionParser.error()</span></code> to signal an application-defined error

  857. condition:</p>

  858. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  859. <span class="o">...</span>

  860. <span class="k">if</span> <span class="n">options</span><span class="o">.</span><span class="n">a</span> <span class="ow">and</span> <span class="n">options</span><span class="o">.</span><span class="n">b</span><span class="p">:</span>

  861.     <span class="n">parser</span><span class="o">.</span><span class="n">error</span><span class="p">(</span><span class="s2">&quot;options -a and -b are mutually exclusive&quot;</span><span class="p">)</span>

  862. </pre></div>

  863. </div>

  864. <p>In either case, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> handles the error the same way: it prints the

  865. program’s usage message and an error message to standard error and exits with

  866. error status 2.</p>

  867. <p>Consider the first example above, where the user passes <code class="docutils literal notranslate"><span class="pre">4x</span></code> to an option

  868. that takes an integer:</p>

  869. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>/usr/bin/foo<span class="w"> </span>-n<span class="w"> </span>4x

  870. <span class="go">Usage: foo [options]</span>

  871. 

  872. <span class="go">foo: error: option -n: invalid integer value: &#39;4x&#39;</span>

  873. </pre></div>

  874. </div>

  875. <p>Or, where the user fails to pass a value at all:</p>

  876. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>/usr/bin/foo<span class="w"> </span>-n

  877. <span class="go">Usage: foo [options]</span>

  878. 

  879. <span class="go">foo: error: -n option requires an argument</span>

  880. </pre></div>

  881. </div>

  882. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>-generated error messages take care always to mention the

  883. option involved in the error; be sure to do the same when calling

  884. <code class="xref py py-func docutils literal notranslate"><span class="pre">OptionParser.error()</span></code> from your application code.</p>

  885. <p>If <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s default error-handling behaviour does not suit your needs,

  886. you’ll need to subclass OptionParser and override its <code class="xref py py-meth docutils literal notranslate"><span class="pre">exit()</span></code>

  887. and/or <code class="xref py py-meth docutils literal notranslate"><span class="pre">error()</span></code> methods.</p>

  888. </section>

  889. <section id="putting-it-all-together">

  890. <span id="optparse-putting-it-all-together"></span><h3>Putting it all together<a class="headerlink" href="#putting-it-all-together" title="Link to this heading">¶</a></h3>

  891. <p>Here’s what <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>-based scripts usually look like:</p>

  892. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">optparse</span> <span class="kn">import</span> <span class="n">OptionParser</span>

  893. <span class="o">...</span>

  894. <span class="k">def</span> <span class="nf">main</span><span class="p">():</span>

  895.     <span class="n">usage</span> <span class="o">=</span> <span class="s2">&quot;usage: %prog [options] arg&quot;</span>

  896.     <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">usage</span><span class="p">)</span>

  897.     <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">,</span>

  898.                       <span class="n">help</span><span class="o">=</span><span class="s2">&quot;read data from FILENAME&quot;</span><span class="p">)</span>

  899.     <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="s2">&quot;--verbose&quot;</span><span class="p">,</span>

  900.                       <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  901.     <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="s2">&quot;--quiet&quot;</span><span class="p">,</span>

  902.                       <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  903.     <span class="o">...</span>

  904.     <span class="p">(</span><span class="n">options</span><span class="p">,</span> <span class="n">args</span><span class="p">)</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  905.     <span class="k">if</span> <span class="nb">len</span><span class="p">(</span><span class="n">args</span><span class="p">)</span> <span class="o">!=</span> <span class="mi">1</span><span class="p">:</span>

  906.         <span class="n">parser</span><span class="o">.</span><span class="n">error</span><span class="p">(</span><span class="s2">&quot;incorrect number of arguments&quot;</span><span class="p">)</span>

  907.     <span class="k">if</span> <span class="n">options</span><span class="o">.</span><span class="n">verbose</span><span class="p">:</span>

  908.         <span class="nb">print</span><span class="p">(</span><span class="s2">&quot;reading </span><span class="si">%s</span><span class="s2">...&quot;</span> <span class="o">%</span> <span class="n">options</span><span class="o">.</span><span class="n">filename</span><span class="p">)</span>

  909.     <span class="o">...</span>

  910. 

  911. <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">&quot;__main__&quot;</span><span class="p">:</span>

  912.     <span class="n">main</span><span class="p">()</span>

  913. </pre></div>

  914. </div>

  915. </section>

  916. </section>

  917. <section id="reference-guide">

  918. <span id="optparse-reference-guide"></span><h2>Reference Guide<a class="headerlink" href="#reference-guide" title="Link to this heading">¶</a></h2>

  919. <section id="creating-the-parser">

  920. <span id="optparse-creating-parser"></span><h3>Creating the parser<a class="headerlink" href="#creating-the-parser" title="Link to this heading">¶</a></h3>

  921. <p>The first step in using <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> is to create an OptionParser instance.</p>

  922. <dl class="py class">

  923. <dt class="sig sig-object py" id="optparse.OptionParser">

  924. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">OptionParser</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">...</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser" title="Link to this definition">¶</a></dt>

  925. <dd><p>The OptionParser constructor has no required arguments, but a number of

  926. optional keyword arguments.  You should always pass them as keyword

  927. arguments, i.e. do not rely on the order in which the arguments are declared.</p>

  928. <dl class="simple">

  929. <dt><code class="docutils literal notranslate"><span class="pre">usage</span></code> (default: <code class="docutils literal notranslate"><span class="pre">&quot;%prog</span> <span class="pre">[options]&quot;</span></code>)</dt><dd><p>The usage summary to print when your program is run incorrectly or with a

  930. help option.  When <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> prints the usage string, it expands

  931. <code class="docutils literal notranslate"><span class="pre">%prog</span></code> to <code class="docutils literal notranslate"><span class="pre">os.path.basename(sys.argv[0])</span></code> (or to <code class="docutils literal notranslate"><span class="pre">prog</span></code> if you

  932. passed that keyword argument).  To suppress a usage message, pass the

  933. special value <code class="xref py py-const docutils literal notranslate"><span class="pre">optparse.SUPPRESS_USAGE</span></code>.</p>

  934. </dd>

  935. <dt><code class="docutils literal notranslate"><span class="pre">option_list</span></code> (default: <code class="docutils literal notranslate"><span class="pre">[]</span></code>)</dt><dd><p>A list of Option objects to populate the parser with.  The options in

  936. <code class="docutils literal notranslate"><span class="pre">option_list</span></code> are added after any options in <code class="docutils literal notranslate"><span class="pre">standard_option_list</span></code> (a

  937. class attribute that may be set by OptionParser subclasses), but before

  938. any version or help options. Deprecated; use <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code></a> after

  939. creating the parser instead.</p>

  940. </dd>

  941. <dt><code class="docutils literal notranslate"><span class="pre">option_class</span></code> (default: optparse.Option)</dt><dd><p>Class to use when adding options to the parser in <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code></a>.</p>

  942. </dd>

  943. <dt><code class="docutils literal notranslate"><span class="pre">version</span></code> (default: <code class="docutils literal notranslate"><span class="pre">None</span></code>)</dt><dd><p>A version string to print when the user supplies a version option. If you

  944. supply a true value for <code class="docutils literal notranslate"><span class="pre">version</span></code>, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> automatically adds a

  945. version option with the single option string <code class="docutils literal notranslate"><span class="pre">--version</span></code>.  The

  946. substring <code class="docutils literal notranslate"><span class="pre">%prog</span></code> is expanded the same as for <code class="docutils literal notranslate"><span class="pre">usage</span></code>.</p>

  947. </dd>

  948. <dt><code class="docutils literal notranslate"><span class="pre">conflict_handler</span></code> (default: <code class="docutils literal notranslate"><span class="pre">&quot;error&quot;</span></code>)</dt><dd><p>Specifies what to do when options with conflicting option strings are

  949. added to the parser; see section

  950. <a class="reference internal" href="#optparse-conflicts-between-options"><span class="std std-ref">Conflicts between options</span></a>.</p>

  951. </dd>

  952. <dt><code class="docutils literal notranslate"><span class="pre">description</span></code> (default: <code class="docutils literal notranslate"><span class="pre">None</span></code>)</dt><dd><p>A paragraph of text giving a brief overview of your program.

  953. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> reformats this paragraph to fit the current terminal width

  954. and prints it when the user requests help (after <code class="docutils literal notranslate"><span class="pre">usage</span></code>, but before the

  955. list of options).</p>

  956. </dd>

  957. <dt><code class="docutils literal notranslate"><span class="pre">formatter</span></code> (default: a new <code class="xref py py-class docutils literal notranslate"><span class="pre">IndentedHelpFormatter</span></code>)</dt><dd><p>An instance of optparse.HelpFormatter that will be used for printing help

  958. text.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> provides two concrete classes for this purpose:

  959. IndentedHelpFormatter and TitledHelpFormatter.</p>

  960. </dd>

  961. <dt><code class="docutils literal notranslate"><span class="pre">add_help_option</span></code> (default: <code class="docutils literal notranslate"><span class="pre">True</span></code>)</dt><dd><p>If true, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will add a help option (with option strings <code class="docutils literal notranslate"><span class="pre">-h</span></code>

  962. and <code class="docutils literal notranslate"><span class="pre">--help</span></code>) to the parser.</p>

  963. </dd>

  964. <dt><code class="docutils literal notranslate"><span class="pre">prog</span></code></dt><dd><p>The string to use when expanding <code class="docutils literal notranslate"><span class="pre">%prog</span></code> in <code class="docutils literal notranslate"><span class="pre">usage</span></code> and <code class="docutils literal notranslate"><span class="pre">version</span></code>

  965. instead of <code class="docutils literal notranslate"><span class="pre">os.path.basename(sys.argv[0])</span></code>.</p>

  966. </dd>

  967. <dt><code class="docutils literal notranslate"><span class="pre">epilog</span></code> (default: <code class="docutils literal notranslate"><span class="pre">None</span></code>)</dt><dd><p>A paragraph of help text to print after the option help.</p>

  968. </dd>

  969. </dl>

  970. </dd></dl>

  971. 

  972. </section>

  973. <section id="populating-the-parser">

  974. <span id="optparse-populating-parser"></span><h3>Populating the parser<a class="headerlink" href="#populating-the-parser" title="Link to this heading">¶</a></h3>

  975. <p>There are several ways to populate the parser with options.  The preferred way

  976. is by using <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a>, as shown in section

  977. <a class="reference internal" href="#optparse-tutorial"><span class="std std-ref">Tutorial</span></a>.  <code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code> can be called in one of two ways:</p>

  978. <ul class="simple">

  979. <li><p>pass it an Option instance (as returned by <code class="xref py py-func docutils literal notranslate"><span class="pre">make_option()</span></code>)</p></li>

  980. <li><p>pass it any combination of positional and keyword arguments that are

  981. acceptable to <code class="xref py py-func docutils literal notranslate"><span class="pre">make_option()</span></code> (i.e., to the Option constructor), and it

  982. will create the Option instance for you</p></li>

  983. </ul>

  984. <p>The other alternative is to pass a list of pre-constructed Option instances to

  985. the OptionParser constructor, as in:</p>

  986. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">option_list</span> <span class="o">=</span> <span class="p">[</span>

  987.     <span class="n">make_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--filename&quot;</span><span class="p">,</span>

  988.                 <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;string&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">),</span>

  989.     <span class="n">make_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="s2">&quot;--quiet&quot;</span><span class="p">,</span>

  990.                 <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">),</span>

  991.     <span class="p">]</span>

  992. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">option_list</span><span class="o">=</span><span class="n">option_list</span><span class="p">)</span>

  993. </pre></div>

  994. </div>

  995. <p>(<code class="xref py py-func docutils literal notranslate"><span class="pre">make_option()</span></code> is a factory function for creating Option instances;

  996. currently it is an alias for the Option constructor.  A future version of

  997. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> may split Option into several classes, and <code class="xref py py-func docutils literal notranslate"><span class="pre">make_option()</span></code>

  998. will pick the right class to instantiate.  Do not instantiate Option directly.)</p>

  999. </section>

  1000. <section id="defining-options">

  1001. <span id="optparse-defining-options"></span><h3>Defining options<a class="headerlink" href="#defining-options" title="Link to this heading">¶</a></h3>

  1002. <p>Each Option instance represents a set of synonymous command-line option strings,

  1003. e.g. <code class="docutils literal notranslate"><span class="pre">-f</span></code> and <code class="docutils literal notranslate"><span class="pre">--file</span></code>.  You can specify any number of short or

  1004. long option strings, but you must specify at least one overall option string.</p>

  1005. <p>The canonical way to create an <a class="reference internal" href="#optparse.Option" title="optparse.Option"><code class="xref py py-class docutils literal notranslate"><span class="pre">Option</span></code></a> instance is with the

  1006. <code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code> method of <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>.</p>

  1007. <dl class="py method">

  1008. <dt class="sig sig-object py" id="optparse.OptionParser.add_option">

  1009. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">add_option</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">option</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.add_option" title="Link to this definition">¶</a></dt>

  1010. <dt class="sig sig-object py">

  1011. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">add_option</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">*opt_str</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">attr=value</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">...</span></span></em><span class="sig-paren">)</span></dt>

  1012. <dd><p>To define an option with only a short option string:</p>

  1013. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="n">attr</span><span class="o">=</span><span class="n">value</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  1014. </pre></div>

  1015. </div>

  1016. <p>And to define an option with only a long option string:</p>

  1017. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--foo&quot;</span><span class="p">,</span> <span class="n">attr</span><span class="o">=</span><span class="n">value</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  1018. </pre></div>

  1019. </div>

  1020. <p>The keyword arguments define attributes of the new Option object.  The most

  1021. important option attribute is <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a>, and it largely

  1022. determines which other attributes are relevant or required.  If you pass

  1023. irrelevant option attributes, or fail to pass required ones, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  1024. raises an <a class="reference internal" href="#optparse.OptionError" title="optparse.OptionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionError</span></code></a> exception explaining your mistake.</p>

  1025. <p>An option’s <em>action</em> determines what <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> does when it encounters

  1026. this option on the command-line.  The standard option actions hard-coded into

  1027. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> are:</p>

  1028. <dl class="simple">

  1029. <dt><code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code></dt><dd><p>store this option’s argument (default)</p>

  1030. </dd>

  1031. <dt><code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code></dt><dd><p>store a constant value, pre-set via <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Option.const</span></code></a></p>

  1032. </dd>

  1033. <dt><code class="docutils literal notranslate"><span class="pre">&quot;store_true&quot;</span></code></dt><dd><p>store <code class="docutils literal notranslate"><span class="pre">True</span></code></p>

  1034. </dd>

  1035. <dt><code class="docutils literal notranslate"><span class="pre">&quot;store_false&quot;</span></code></dt><dd><p>store <code class="docutils literal notranslate"><span class="pre">False</span></code></p>

  1036. </dd>

  1037. <dt><code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code></dt><dd><p>append this option’s argument to a list</p>

  1038. </dd>

  1039. <dt><code class="docutils literal notranslate"><span class="pre">&quot;append_const&quot;</span></code></dt><dd><p>append a constant value to a list, pre-set via <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Option.const</span></code></a></p>

  1040. </dd>

  1041. <dt><code class="docutils literal notranslate"><span class="pre">&quot;count&quot;</span></code></dt><dd><p>increment a counter by one</p>

  1042. </dd>

  1043. <dt><code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code></dt><dd><p>call a specified function</p>

  1044. </dd>

  1045. <dt><code class="docutils literal notranslate"><span class="pre">&quot;help&quot;</span></code></dt><dd><p>print a usage message including all options and the documentation for them</p>

  1046. </dd>

  1047. </dl>

  1048. <p>(If you don’t supply an action, the default is <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code>.  For this action,

  1049. you may also supply <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> and <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> option

  1050. attributes; see <a class="reference internal" href="#optparse-standard-option-actions"><span class="std std-ref">Standard option actions</span></a>.)</p>

  1051. </dd></dl>

  1052. 

  1053. <p>As you can see, most actions involve storing or updating a value somewhere.

  1054. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> always creates a special object for this, conventionally called

  1055. <code class="docutils literal notranslate"><span class="pre">options</span></code>, which is an instance of <a class="reference internal" href="#optparse.Values" title="optparse.Values"><code class="xref py py-class docutils literal notranslate"><span class="pre">optparse.Values</span></code></a>.</p>

  1056. <dl class="py class">

  1057. <dt class="sig sig-object py" id="optparse.Values">

  1058. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">Values</span></span><a class="headerlink" href="#optparse.Values" title="Link to this definition">¶</a></dt>

  1059. <dd><p>An object holding parsed argument names and values as attributes.

  1060. Normally created by calling when calling <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.parse_args()</span></code></a>,

  1061. and can be overridden by a custom subclass passed to the <em>values</em> argument of

  1062. <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.parse_args()</span></code></a> (as described in <a class="reference internal" href="#optparse-parsing-arguments"><span class="std std-ref">Parsing arguments</span></a>).</p>

  1063. </dd></dl>

  1064. 

  1065. <p>Option

  1066. arguments (and various other values) are stored as attributes of this object,

  1067. according to the <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> (destination) option attribute.</p>

  1068. <p>For example, when you call</p>

  1069. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">()</span>

  1070. </pre></div>

  1071. </div>

  1072. <p>one of the first things <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> does is create the <code class="docutils literal notranslate"><span class="pre">options</span></code> object:</p>

  1073. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span> <span class="o">=</span> <span class="n">Values</span><span class="p">()</span>

  1074. </pre></div>

  1075. </div>

  1076. <p>If one of the options in this parser is defined with</p>

  1077. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">,</span> <span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;string&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">)</span>

  1078. </pre></div>

  1079. </div>

  1080. <p>and the command-line being parsed includes any of the following:</p>

  1081. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-</span><span class="n">ffoo</span>

  1082. <span class="o">-</span><span class="n">f</span> <span class="n">foo</span>

  1083. <span class="o">--</span><span class="n">file</span><span class="o">=</span><span class="n">foo</span>

  1084. <span class="o">--</span><span class="n">file</span> <span class="n">foo</span>

  1085. </pre></div>

  1086. </div>

  1087. <p>then <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, on seeing this option, will do the equivalent of</p>

  1088. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">filename</span> <span class="o">=</span> <span class="s2">&quot;foo&quot;</span>

  1089. </pre></div>

  1090. </div>

  1091. <p>The <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> and <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> option attributes are almost

  1092. as important as <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a>, but <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a> is the only

  1093. one that makes sense for <em>all</em> options.</p>

  1094. </section>

  1095. <section id="option-attributes">

  1096. <span id="optparse-option-attributes"></span><h3>Option attributes<a class="headerlink" href="#option-attributes" title="Link to this heading">¶</a></h3>

  1097. <dl class="py class">

  1098. <dt class="sig sig-object py" id="optparse.Option">

  1099. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">Option</span></span><a class="headerlink" href="#optparse.Option" title="Link to this definition">¶</a></dt>

  1100. <dd><p>A single command line argument,

  1101. with various attributes passed by keyword to the constructor.

  1102. Normally created with <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a> rather than directly,

  1103. and can be overridden by a custom class via the <em>option_class</em> argument

  1104. to <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>.</p>

  1105. </dd></dl>

  1106. 

  1107. <p>The following option attributes may be passed as keyword arguments to

  1108. <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a>.  If you pass an option attribute that is not

  1109. relevant to a particular option, or fail to pass a required option attribute,

  1110. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> raises <a class="reference internal" href="#optparse.OptionError" title="optparse.OptionError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionError</span></code></a>.</p>

  1111. <dl class="py attribute">

  1112. <dt class="sig sig-object py" id="optparse.Option.action">

  1113. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">action</span></span><a class="headerlink" href="#optparse.Option.action" title="Link to this definition">¶</a></dt>

  1114. <dd><p>(default: <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code>)</p>

  1115. <p>Determines <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s behaviour when this option is seen on the

  1116. command line; the available options are documented <a class="reference internal" href="#optparse-standard-option-actions"><span class="std std-ref">here</span></a>.</p>

  1117. </dd></dl>

  1118. 

  1119. <dl class="py attribute">

  1120. <dt class="sig sig-object py" id="optparse.Option.type">

  1121. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">type</span></span><a class="headerlink" href="#optparse.Option.type" title="Link to this definition">¶</a></dt>

  1122. <dd><p>(default: <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code>)</p>

  1123. <p>The argument type expected by this option (e.g., <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code> or <code class="docutils literal notranslate"><span class="pre">&quot;int&quot;</span></code>);

  1124. the available option types are documented <a class="reference internal" href="#optparse-standard-option-types"><span class="std std-ref">here</span></a>.</p>

  1125. </dd></dl>

  1126. 

  1127. <dl class="py attribute">

  1128. <dt class="sig sig-object py" id="optparse.Option.dest">

  1129. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">dest</span></span><a class="headerlink" href="#optparse.Option.dest" title="Link to this definition">¶</a></dt>

  1130. <dd><p>(default: derived from option strings)</p>

  1131. <p>If the option’s action implies writing or modifying a value somewhere, this

  1132. tells <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> where to write it: <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> names an

  1133. attribute of the <code class="docutils literal notranslate"><span class="pre">options</span></code> object that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> builds as it parses

  1134. the command line.</p>

  1135. </dd></dl>

  1136. 

  1137. <dl class="py attribute">

  1138. <dt class="sig sig-object py" id="optparse.Option.default">

  1139. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">default</span></span><a class="headerlink" href="#optparse.Option.default" title="Link to this definition">¶</a></dt>

  1140. <dd><p>The value to use for this option’s destination if the option is not seen on

  1141. the command line.  See also <a class="reference internal" href="#optparse.OptionParser.set_defaults" title="optparse.OptionParser.set_defaults"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.set_defaults()</span></code></a>.</p>

  1142. </dd></dl>

  1143. 

  1144. <dl class="py attribute">

  1145. <dt class="sig sig-object py" id="optparse.Option.nargs">

  1146. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">nargs</span></span><a class="headerlink" href="#optparse.Option.nargs" title="Link to this definition">¶</a></dt>

  1147. <dd><p>(default: 1)</p>

  1148. <p>How many arguments of type <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> should be consumed when this

  1149. option is seen.  If &gt; 1, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will store a tuple of values to

  1150. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.</p>

  1151. </dd></dl>

  1152. 

  1153. <dl class="py attribute">

  1154. <dt class="sig sig-object py" id="optparse.Option.const">

  1155. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">const</span></span><a class="headerlink" href="#optparse.Option.const" title="Link to this definition">¶</a></dt>

  1156. <dd><p>For actions that store a constant value, the constant value to store.</p>

  1157. </dd></dl>

  1158. 

  1159. <dl class="py attribute">

  1160. <dt class="sig sig-object py" id="optparse.Option.choices">

  1161. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">choices</span></span><a class="headerlink" href="#optparse.Option.choices" title="Link to this definition">¶</a></dt>

  1162. <dd><p>For options of type <code class="docutils literal notranslate"><span class="pre">&quot;choice&quot;</span></code>, the list of strings the user may choose

  1163. from.</p>

  1164. </dd></dl>

  1165. 

  1166. <dl class="py attribute">

  1167. <dt class="sig sig-object py" id="optparse.Option.callback">

  1168. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">callback</span></span><a class="headerlink" href="#optparse.Option.callback" title="Link to this definition">¶</a></dt>

  1169. <dd><p>For options with action <code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code>, the callable to call when this option

  1170. is seen.  See section <a class="reference internal" href="#optparse-option-callbacks"><span class="std std-ref">Option Callbacks</span></a> for detail on the

  1171. arguments passed to the callable.</p>

  1172. </dd></dl>

  1173. 

  1174. <dl class="py attribute">

  1175. <dt class="sig sig-object py" id="optparse.Option.callback_args">

  1176. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">callback_args</span></span><a class="headerlink" href="#optparse.Option.callback_args" title="Link to this definition">¶</a></dt>

  1177. <dt class="sig sig-object py" id="optparse.Option.callback_kwargs">

  1178. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">callback_kwargs</span></span><a class="headerlink" href="#optparse.Option.callback_kwargs" title="Link to this definition">¶</a></dt>

  1179. <dd><p>Additional positional and keyword arguments to pass to <code class="docutils literal notranslate"><span class="pre">callback</span></code> after the

  1180. four standard callback arguments.</p>

  1181. </dd></dl>

  1182. 

  1183. <dl class="py attribute">

  1184. <dt class="sig sig-object py" id="optparse.Option.help">

  1185. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">help</span></span><a class="headerlink" href="#optparse.Option.help" title="Link to this definition">¶</a></dt>

  1186. <dd><p>Help text to print for this option when listing all available options after

  1187. the user supplies a <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> option (such as <code class="docutils literal notranslate"><span class="pre">--help</span></code>).  If

  1188. no help text is supplied, the option will be listed without help text.  To

  1189. hide this option, use the special value <code class="xref py py-const docutils literal notranslate"><span class="pre">optparse.SUPPRESS_HELP</span></code>.</p>

  1190. </dd></dl>

  1191. 

  1192. <dl class="py attribute">

  1193. <dt class="sig sig-object py" id="optparse.Option.metavar">

  1194. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">metavar</span></span><a class="headerlink" href="#optparse.Option.metavar" title="Link to this definition">¶</a></dt>

  1195. <dd><p>(default: derived from option strings)</p>

  1196. <p>Stand-in for the option argument(s) to use when printing help text.  See

  1197. section <a class="reference internal" href="#optparse-tutorial"><span class="std std-ref">Tutorial</span></a> for an example.</p>

  1198. </dd></dl>

  1199. 

  1200. </section>

  1201. <section id="standard-option-actions">

  1202. <span id="optparse-standard-option-actions"></span><h3>Standard option actions<a class="headerlink" href="#standard-option-actions" title="Link to this heading">¶</a></h3>

  1203. <p>The various option actions all have slightly different requirements and effects.

  1204. Most actions have several relevant option attributes which you may specify to

  1205. guide <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s behaviour; a few have required attributes, which you

  1206. must specify for any option using that action.</p>

  1207. <ul>

  1208. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code> [relevant: <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>, <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>,

  1209. <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>, <a class="reference internal" href="#optparse.Option.choices" title="optparse.Option.choices"><code class="xref py py-attr docutils literal notranslate"><span class="pre">choices</span></code></a>]</p>

  1210. <p>The option must be followed by an argument, which is converted to a value

  1211. according to <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> and stored in <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.  If

  1212. <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a> &gt; 1, multiple arguments will be consumed from the

  1213. command line; all will be converted according to <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> and

  1214. stored to <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> as a tuple.  See the

  1215. <a class="reference internal" href="#optparse-standard-option-types"><span class="std std-ref">Standard option types</span></a> section.</p>

  1216. <p>If <a class="reference internal" href="#optparse.Option.choices" title="optparse.Option.choices"><code class="xref py py-attr docutils literal notranslate"><span class="pre">choices</span></code></a> is supplied (a list or tuple of strings), the type

  1217. defaults to <code class="docutils literal notranslate"><span class="pre">&quot;choice&quot;</span></code>.</p>

  1218. <p>If <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> is not supplied, it defaults to <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code>.</p>

  1219. <p>If <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> is not supplied, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> derives a destination

  1220. from the first long option string (e.g., <code class="docutils literal notranslate"><span class="pre">--foo-bar</span></code> implies

  1221. <code class="docutils literal notranslate"><span class="pre">foo_bar</span></code>). If there are no long option strings, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> derives a

  1222. destination from the first short option string (e.g., <code class="docutils literal notranslate"><span class="pre">-f</span></code> implies <code class="docutils literal notranslate"><span class="pre">f</span></code>).</p>

  1223. <p>Example:</p>

  1224. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-f&quot;</span><span class="p">)</span>

  1225. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-p&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;float&quot;</span><span class="p">,</span> <span class="n">nargs</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;point&quot;</span><span class="p">)</span>

  1226. </pre></div>

  1227. </div>

  1228. <p>As it parses the command line</p>

  1229. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">-</span><span class="n">f</span> <span class="n">foo</span><span class="o">.</span><span class="n">txt</span> <span class="o">-</span><span class="n">p</span> <span class="mi">1</span> <span class="o">-</span><span class="mf">3.5</span> <span class="mi">4</span> <span class="o">-</span><span class="n">fbar</span><span class="o">.</span><span class="n">txt</span>

  1230. </pre></div>

  1231. </div>

  1232. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will set</p>

  1233. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">f</span> <span class="o">=</span> <span class="s2">&quot;foo.txt&quot;</span>

  1234. <span class="n">options</span><span class="o">.</span><span class="n">point</span> <span class="o">=</span> <span class="p">(</span><span class="mf">1.0</span><span class="p">,</span> <span class="o">-</span><span class="mf">3.5</span><span class="p">,</span> <span class="mf">4.0</span><span class="p">)</span>

  1235. <span class="n">options</span><span class="o">.</span><span class="n">f</span> <span class="o">=</span> <span class="s2">&quot;bar.txt&quot;</span>

  1236. </pre></div>

  1237. </div>

  1238. </li>

  1239. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code> [required: <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">const</span></code></a>; relevant:

  1240. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>]</p>

  1241. <p>The value <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">const</span></code></a> is stored in <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.</p>

  1242. <p>Example:</p>

  1243. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-q&quot;</span><span class="p">,</span> <span class="s2">&quot;--quiet&quot;</span><span class="p">,</span>

  1244.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="mi">0</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  1245. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="s2">&quot;--verbose&quot;</span><span class="p">,</span>

  1246.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="mi">1</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  1247. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--noisy&quot;</span><span class="p">,</span>

  1248.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="mi">2</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">)</span>

  1249. </pre></div>

  1250. </div>

  1251. <p>If <code class="docutils literal notranslate"><span class="pre">--noisy</span></code> is seen, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will set</p>

  1252. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">verbose</span> <span class="o">=</span> <span class="mi">2</span>

  1253. </pre></div>

  1254. </div>

  1255. </li>

  1256. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;store_true&quot;</span></code> [relevant: <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>]</p>

  1257. <p>A special case of <code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code> that stores <code class="docutils literal notranslate"><span class="pre">True</span></code> to

  1258. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.</p>

  1259. </li>

  1260. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;store_false&quot;</span></code> [relevant: <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>]</p>

  1261. <p>Like <code class="docutils literal notranslate"><span class="pre">&quot;store_true&quot;</span></code>, but stores <code class="docutils literal notranslate"><span class="pre">False</span></code>.</p>

  1262. <p>Example:</p>

  1263. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--clobber&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;clobber&quot;</span><span class="p">)</span>

  1264. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--no-clobber&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_false&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;clobber&quot;</span><span class="p">)</span>

  1265. </pre></div>

  1266. </div>

  1267. </li>

  1268. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code> [relevant: <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>, <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>,

  1269. <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>, <a class="reference internal" href="#optparse.Option.choices" title="optparse.Option.choices"><code class="xref py py-attr docutils literal notranslate"><span class="pre">choices</span></code></a>]</p>

  1270. <p>The option must be followed by an argument, which is appended to the list in

  1271. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.  If no default value for <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> is

  1272. supplied, an empty list is automatically created when <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> first

  1273. encounters this option on the command-line.  If <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a> &gt; 1,

  1274. multiple arguments are consumed, and a tuple of length <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>

  1275. is appended to <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.</p>

  1276. <p>The defaults for <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> and <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> are the same as

  1277. for the <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code> action.</p>

  1278. <p>Example:</p>

  1279. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-t&quot;</span><span class="p">,</span> <span class="s2">&quot;--tracks&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;append&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;int&quot;</span><span class="p">)</span>

  1280. </pre></div>

  1281. </div>

  1282. <p>If <code class="docutils literal notranslate"><span class="pre">-t3</span></code> is seen on the command-line, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> does the equivalent

  1283. of:</p>

  1284. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">tracks</span> <span class="o">=</span> <span class="p">[]</span>

  1285. <span class="n">options</span><span class="o">.</span><span class="n">tracks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="s2">&quot;3&quot;</span><span class="p">))</span>

  1286. </pre></div>

  1287. </div>

  1288. <p>If, a little later on, <code class="docutils literal notranslate"><span class="pre">--tracks=4</span></code> is seen, it does:</p>

  1289. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">tracks</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="nb">int</span><span class="p">(</span><span class="s2">&quot;4&quot;</span><span class="p">))</span>

  1290. </pre></div>

  1291. </div>

  1292. <p>The <code class="docutils literal notranslate"><span class="pre">append</span></code> action calls the <code class="docutils literal notranslate"><span class="pre">append</span></code> method on the current value of the

  1293. option.  This means that any default value specified must have an <code class="docutils literal notranslate"><span class="pre">append</span></code>

  1294. method.  It also means that if the default value is non-empty, the default

  1295. elements will be present in the parsed value for the option, with any values

  1296. from the command line appended after those default values:</p>

  1297. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--files&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;append&quot;</span><span class="p">,</span> <span class="n">default</span><span class="o">=</span><span class="p">[</span><span class="s1">&#39;~/.mypkg/defaults&#39;</span><span class="p">])</span>

  1298. <span class="gp">&gt;&gt;&gt; </span><span class="n">opts</span><span class="p">,</span> <span class="n">args</span> <span class="o">=</span> <span class="n">parser</span><span class="o">.</span><span class="n">parse_args</span><span class="p">([</span><span class="s1">&#39;--files&#39;</span><span class="p">,</span> <span class="s1">&#39;overrides.mypkg&#39;</span><span class="p">])</span>

  1299. <span class="gp">&gt;&gt;&gt; </span><span class="n">opts</span><span class="o">.</span><span class="n">files</span>

  1300. <span class="go">[&#39;~/.mypkg/defaults&#39;, &#39;overrides.mypkg&#39;]</span>

  1301. </pre></div>

  1302. </div>

  1303. </li>

  1304. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;append_const&quot;</span></code> [required: <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">const</span></code></a>; relevant:

  1305. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>]</p>

  1306. <p>Like <code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code>, but the value <a class="reference internal" href="#optparse.Option.const" title="optparse.Option.const"><code class="xref py py-attr docutils literal notranslate"><span class="pre">const</span></code></a> is appended to

  1307. <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>; as with <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code>, <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> defaults to

  1308. <code class="docutils literal notranslate"><span class="pre">None</span></code>, and an empty list is automatically created the first time the option

  1309. is encountered.</p>

  1310. </li>

  1311. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;count&quot;</span></code> [relevant: <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>]</p>

  1312. <p>Increment the integer stored at <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>.  If no default value is

  1313. supplied, <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a> is set to zero before being incremented the

  1314. first time.</p>

  1315. <p>Example:</p>

  1316. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;count&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbosity&quot;</span><span class="p">)</span>

  1317. </pre></div>

  1318. </div>

  1319. <p>The first time <code class="docutils literal notranslate"><span class="pre">-v</span></code> is seen on the command line, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> does the

  1320. equivalent of:</p>

  1321. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">verbosity</span> <span class="o">=</span> <span class="mi">0</span>

  1322. <span class="n">options</span><span class="o">.</span><span class="n">verbosity</span> <span class="o">+=</span> <span class="mi">1</span>

  1323. </pre></div>

  1324. </div>

  1325. <p>Every subsequent occurrence of <code class="docutils literal notranslate"><span class="pre">-v</span></code> results in</p>

  1326. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">options</span><span class="o">.</span><span class="n">verbosity</span> <span class="o">+=</span> <span class="mi">1</span>

  1327. </pre></div>

  1328. </div>

  1329. </li>

  1330. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code> [required: <a class="reference internal" href="#optparse.Option.callback" title="optparse.Option.callback"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback</span></code></a>; relevant:

  1331. <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>, <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>, <a class="reference internal" href="#optparse.Option.callback_args" title="optparse.Option.callback_args"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_args</span></code></a>,

  1332. <a class="reference internal" href="#optparse.Option.callback_kwargs" title="optparse.Option.callback_kwargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_kwargs</span></code></a>]</p>

  1333. <p>Call the function specified by <a class="reference internal" href="#optparse.Option.callback" title="optparse.Option.callback"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback</span></code></a>, which is called as</p>

  1334. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">func</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>

  1335. </pre></div>

  1336. </div>

  1337. <p>See section <a class="reference internal" href="#optparse-option-callbacks"><span class="std std-ref">Option Callbacks</span></a> for more detail.</p>

  1338. </li>

  1339. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;help&quot;</span></code></p>

  1340. <p>Prints a complete help message for all the options in the current option

  1341. parser.  The help message is constructed from the <code class="docutils literal notranslate"><span class="pre">usage</span></code> string passed to

  1342. OptionParser’s constructor and the <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> string passed to every

  1343. option.</p>

  1344. <p>If no <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> string is supplied for an option, it will still be

  1345. listed in the help message.  To omit an option entirely, use the special value

  1346. <code class="xref py py-const docutils literal notranslate"><span class="pre">optparse.SUPPRESS_HELP</span></code>.</p>

  1347. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> automatically adds a <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> option to all

  1348. OptionParsers, so you do not normally need to create one.</p>

  1349. <p>Example:</p>

  1350. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">optparse</span> <span class="kn">import</span> <span class="n">OptionParser</span><span class="p">,</span> <span class="n">SUPPRESS_HELP</span>

  1351. 

  1352. <span class="c1"># usually, a help option is added automatically, but that can</span>

  1353. <span class="c1"># be suppressed using the add_help_option argument</span>

  1354. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">add_help_option</span><span class="o">=</span><span class="kc">False</span><span class="p">)</span>

  1355. 

  1356. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-h&quot;</span><span class="p">,</span> <span class="s2">&quot;--help&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;help&quot;</span><span class="p">)</span>

  1357. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-v&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;verbose&quot;</span><span class="p">,</span>

  1358.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Be moderately verbose&quot;</span><span class="p">)</span>

  1359. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--file&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;filename&quot;</span><span class="p">,</span>

  1360.                   <span class="n">help</span><span class="o">=</span><span class="s2">&quot;Input file to read data from&quot;</span><span class="p">)</span>

  1361. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--secret&quot;</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="n">SUPPRESS_HELP</span><span class="p">)</span>

  1362. </pre></div>

  1363. </div>

  1364. <p>If <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> sees either <code class="docutils literal notranslate"><span class="pre">-h</span></code> or <code class="docutils literal notranslate"><span class="pre">--help</span></code> on the command line,

  1365. it will print something like the following help message to stdout (assuming

  1366. <code class="docutils literal notranslate"><span class="pre">sys.argv[0]</span></code> is <code class="docutils literal notranslate"><span class="pre">&quot;foo.py&quot;</span></code>):</p>

  1367. <div class="highlight-text notranslate"><div class="highlight"><pre><span></span>Usage: foo.py [options]

  1368. 

  1369. Options:

  1370.   -h, --help        Show this help message and exit

  1371.   -v                Be moderately verbose

  1372.   --file=FILENAME   Input file to read data from

  1373. </pre></div>

  1374. </div>

  1375. <p>After printing the help message, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> terminates your process with

  1376. <code class="docutils literal notranslate"><span class="pre">sys.exit(0)</span></code>.</p>

  1377. </li>

  1378. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;version&quot;</span></code></p>

  1379. <p>Prints the version number supplied to the OptionParser to stdout and exits.

  1380. The version number is actually formatted and printed by the

  1381. <code class="docutils literal notranslate"><span class="pre">print_version()</span></code> method of OptionParser.  Generally only relevant if the

  1382. <code class="docutils literal notranslate"><span class="pre">version</span></code> argument is supplied to the OptionParser constructor.  As with

  1383. <a class="reference internal" href="#optparse.Option.help" title="optparse.Option.help"><code class="xref py py-attr docutils literal notranslate"><span class="pre">help</span></code></a> options, you will rarely create <code class="docutils literal notranslate"><span class="pre">version</span></code> options,

  1384. since <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> automatically adds them when needed.</p>

  1385. </li>

  1386. </ul>

  1387. </section>

  1388. <section id="standard-option-types">

  1389. <span id="optparse-standard-option-types"></span><h3>Standard option types<a class="headerlink" href="#standard-option-types" title="Link to this heading">¶</a></h3>

  1390. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> has five built-in option types: <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code>, <code class="docutils literal notranslate"><span class="pre">&quot;int&quot;</span></code>,

  1391. <code class="docutils literal notranslate"><span class="pre">&quot;choice&quot;</span></code>, <code class="docutils literal notranslate"><span class="pre">&quot;float&quot;</span></code> and <code class="docutils literal notranslate"><span class="pre">&quot;complex&quot;</span></code>.  If you need to add new

  1392. option types, see section <a class="reference internal" href="#optparse-extending-optparse"><span class="std std-ref">Extending optparse</span></a>.</p>

  1393. <p>Arguments to string options are not checked or converted in any way: the text on

  1394. the command line is stored in the destination (or passed to the callback) as-is.</p>

  1395. <p>Integer arguments (type <code class="docutils literal notranslate"><span class="pre">&quot;int&quot;</span></code>) are parsed as follows:</p>

  1396. <ul class="simple">

  1397. <li><p>if the number starts with <code class="docutils literal notranslate"><span class="pre">0x</span></code>, it is parsed as a hexadecimal number</p></li>

  1398. <li><p>if the number starts with <code class="docutils literal notranslate"><span class="pre">0</span></code>, it is parsed as an octal number</p></li>

  1399. <li><p>if the number starts with <code class="docutils literal notranslate"><span class="pre">0b</span></code>, it is parsed as a binary number</p></li>

  1400. <li><p>otherwise, the number is parsed as a decimal number</p></li>

  1401. </ul>

  1402. <p>The conversion is done by calling <a class="reference internal" href="functions.html#int" title="int"><code class="xref py py-func docutils literal notranslate"><span class="pre">int()</span></code></a> with the appropriate base (2, 8,

  1403. 10, or 16).  If this fails, so will <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>, although with a more useful

  1404. error message.</p>

  1405. <p><code class="docutils literal notranslate"><span class="pre">&quot;float&quot;</span></code> and <code class="docutils literal notranslate"><span class="pre">&quot;complex&quot;</span></code> option arguments are converted directly with

  1406. <a class="reference internal" href="functions.html#float" title="float"><code class="xref py py-func docutils literal notranslate"><span class="pre">float()</span></code></a> and <a class="reference internal" href="functions.html#complex" title="complex"><code class="xref py py-func docutils literal notranslate"><span class="pre">complex()</span></code></a>, with similar error-handling.</p>

  1407. <p><code class="docutils literal notranslate"><span class="pre">&quot;choice&quot;</span></code> options are a subtype of <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code> options.  The

  1408. <a class="reference internal" href="#optparse.Option.choices" title="optparse.Option.choices"><code class="xref py py-attr docutils literal notranslate"><span class="pre">choices</span></code></a> option attribute (a sequence of strings) defines the

  1409. set of allowed option arguments.  <code class="xref py py-func docutils literal notranslate"><span class="pre">optparse.check_choice()</span></code> compares

  1410. user-supplied option arguments against this master list and raises

  1411. <a class="reference internal" href="#optparse.OptionValueError" title="optparse.OptionValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionValueError</span></code></a> if an invalid string is given.</p>

  1412. </section>

  1413. <section id="parsing-arguments">

  1414. <span id="optparse-parsing-arguments"></span><h3>Parsing arguments<a class="headerlink" href="#parsing-arguments" title="Link to this heading">¶</a></h3>

  1415. <p>The whole point of creating and populating an OptionParser is to call its

  1416. <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a> method.</p>

  1417. <dl class="py method">

  1418. <dt class="sig sig-object py" id="optparse.OptionParser.parse_args">

  1419. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">parse_args</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">args</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">values</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.parse_args" title="Link to this definition">¶</a></dt>

  1420. <dd><p>Parse the command-line options found in <em>args</em>.</p>

  1421. <p>The input parameters are</p>

  1422. <dl class="simple">

  1423. <dt><code class="docutils literal notranslate"><span class="pre">args</span></code></dt><dd><p>the list of arguments to process (default: <code class="docutils literal notranslate"><span class="pre">sys.argv[1:]</span></code>)</p>

  1424. </dd>

  1425. <dt><code class="docutils literal notranslate"><span class="pre">values</span></code></dt><dd><p>an <a class="reference internal" href="#optparse.Values" title="optparse.Values"><code class="xref py py-class docutils literal notranslate"><span class="pre">Values</span></code></a> object to store option arguments in (default: a

  1426. new instance of <a class="reference internal" href="#optparse.Values" title="optparse.Values"><code class="xref py py-class docutils literal notranslate"><span class="pre">Values</span></code></a>) – if you give an existing object, the

  1427. option defaults will not be initialized on it</p>

  1428. </dd>

  1429. </dl>

  1430. <p>and the return value is a pair <code class="docutils literal notranslate"><span class="pre">(options,</span> <span class="pre">args)</span></code> where</p>

  1431. <dl class="simple">

  1432. <dt><code class="docutils literal notranslate"><span class="pre">options</span></code></dt><dd><p>the same object that was passed in as <em>values</em>, or the <code class="docutils literal notranslate"><span class="pre">optparse.Values</span></code>

  1433. instance created by <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a></p>

  1434. </dd>

  1435. <dt><code class="docutils literal notranslate"><span class="pre">args</span></code></dt><dd><p>the leftover positional arguments after all options have been processed</p>

  1436. </dd>

  1437. </dl>

  1438. </dd></dl>

  1439. 

  1440. <p>The most common usage is to supply neither keyword argument.  If you supply

  1441. <code class="docutils literal notranslate"><span class="pre">values</span></code>, it will be modified with repeated <a class="reference internal" href="functions.html#setattr" title="setattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">setattr()</span></code></a> calls (roughly one

  1442. for every option argument stored to an option destination) and returned by

  1443. <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a>.</p>

  1444. <p>If <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a> encounters any errors in the argument list, it calls the

  1445. OptionParser’s <code class="xref py py-meth docutils literal notranslate"><span class="pre">error()</span></code> method with an appropriate end-user error message.

  1446. This ultimately terminates your process with an exit status of 2 (the

  1447. traditional Unix exit status for command-line errors).</p>

  1448. </section>

  1449. <section id="querying-and-manipulating-your-option-parser">

  1450. <span id="optparse-querying-manipulating-option-parser"></span><h3>Querying and manipulating your option parser<a class="headerlink" href="#querying-and-manipulating-your-option-parser" title="Link to this heading">¶</a></h3>

  1451. <p>The default behavior of the option parser can be customized slightly, and you

  1452. can also poke around your option parser and see what’s there.  OptionParser

  1453. provides several methods to help you out:</p>

  1454. <dl class="py method">

  1455. <dt class="sig sig-object py" id="optparse.OptionParser.disable_interspersed_args">

  1456. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">disable_interspersed_args</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.disable_interspersed_args" title="Link to this definition">¶</a></dt>

  1457. <dd><p>Set parsing to stop on the first non-option.  For example, if <code class="docutils literal notranslate"><span class="pre">-a</span></code> and

  1458. <code class="docutils literal notranslate"><span class="pre">-b</span></code> are both simple options that take no arguments, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  1459. normally accepts this syntax:</p>

  1460. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">prog</span> <span class="o">-</span><span class="n">a</span> <span class="n">arg1</span> <span class="o">-</span><span class="n">b</span> <span class="n">arg2</span>

  1461. </pre></div>

  1462. </div>

  1463. <p>and treats it as equivalent to</p>

  1464. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">prog</span> <span class="o">-</span><span class="n">a</span> <span class="o">-</span><span class="n">b</span> <span class="n">arg1</span> <span class="n">arg2</span>

  1465. </pre></div>

  1466. </div>

  1467. <p>To disable this feature, call <a class="reference internal" href="#optparse.OptionParser.disable_interspersed_args" title="optparse.OptionParser.disable_interspersed_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">disable_interspersed_args()</span></code></a>.  This

  1468. restores traditional Unix syntax, where option parsing stops with the first

  1469. non-option argument.</p>

  1470. <p>Use this if you have a command processor which runs another command which has

  1471. options of its own and you want to make sure these options don’t get

  1472. confused.  For example, each command might have a different set of options.</p>

  1473. </dd></dl>

  1474. 

  1475. <dl class="py method">

  1476. <dt class="sig sig-object py" id="optparse.OptionParser.enable_interspersed_args">

  1477. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">enable_interspersed_args</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.enable_interspersed_args" title="Link to this definition">¶</a></dt>

  1478. <dd><p>Set parsing to not stop on the first non-option, allowing interspersing

  1479. switches with command arguments.  This is the default behavior.</p>

  1480. </dd></dl>

  1481. 

  1482. <dl class="py method">

  1483. <dt class="sig sig-object py" id="optparse.OptionParser.get_option">

  1484. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">get_option</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">opt_str</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.get_option" title="Link to this definition">¶</a></dt>

  1485. <dd><p>Returns the Option instance with the option string <em>opt_str</em>, or <code class="docutils literal notranslate"><span class="pre">None</span></code> if

  1486. no options have that option string.</p>

  1487. </dd></dl>

  1488. 

  1489. <dl class="py method">

  1490. <dt class="sig sig-object py" id="optparse.OptionParser.has_option">

  1491. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">has_option</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">opt_str</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.has_option" title="Link to this definition">¶</a></dt>

  1492. <dd><p>Return <code class="docutils literal notranslate"><span class="pre">True</span></code> if the OptionParser has an option with option string <em>opt_str</em>

  1493. (e.g., <code class="docutils literal notranslate"><span class="pre">-q</span></code> or <code class="docutils literal notranslate"><span class="pre">--verbose</span></code>).</p>

  1494. </dd></dl>

  1495. 

  1496. <dl class="py method">

  1497. <dt class="sig sig-object py" id="optparse.OptionParser.remove_option">

  1498. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">remove_option</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">opt_str</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.remove_option" title="Link to this definition">¶</a></dt>

  1499. <dd><p>If the <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a> has an option corresponding to <em>opt_str</em>, that

  1500. option is removed.  If that option provided any other option strings, all of

  1501. those option strings become invalid. If <em>opt_str</em> does not occur in any

  1502. option belonging to this <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>, raises <a class="reference internal" href="exceptions.html#ValueError" title="ValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ValueError</span></code></a>.</p>

  1503. </dd></dl>

  1504. 

  1505. </section>

  1506. <section id="conflicts-between-options">

  1507. <span id="optparse-conflicts-between-options"></span><h3>Conflicts between options<a class="headerlink" href="#conflicts-between-options" title="Link to this heading">¶</a></h3>

  1508. <p>If you’re not careful, it’s easy to define options with conflicting option

  1509. strings:</p>

  1510. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-n&quot;</span><span class="p">,</span> <span class="s2">&quot;--dry-run&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  1511. <span class="o">...</span>

  1512. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-n&quot;</span><span class="p">,</span> <span class="s2">&quot;--noisy&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">)</span>

  1513. </pre></div>

  1514. </div>

  1515. <p>(This is particularly true if you’ve defined your own OptionParser subclass with

  1516. some standard options.)</p>

  1517. <p>Every time you add an option, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> checks for conflicts with existing

  1518. options.  If it finds any, it invokes the current conflict-handling mechanism.

  1519. You can set the conflict-handling mechanism either in the constructor:</p>

  1520. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="o">...</span><span class="p">,</span> <span class="n">conflict_handler</span><span class="o">=</span><span class="n">handler</span><span class="p">)</span>

  1521. </pre></div>

  1522. </div>

  1523. <p>or with a separate call:</p>

  1524. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">set_conflict_handler</span><span class="p">(</span><span class="n">handler</span><span class="p">)</span>

  1525. </pre></div>

  1526. </div>

  1527. <p>The available conflict handlers are:</p>

  1528. <blockquote>

  1529. <div><dl class="simple">

  1530. <dt><code class="docutils literal notranslate"><span class="pre">&quot;error&quot;</span></code> (default)</dt><dd><p>assume option conflicts are a programming error and raise

  1531. <a class="reference internal" href="#optparse.OptionConflictError" title="optparse.OptionConflictError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionConflictError</span></code></a></p>

  1532. </dd>

  1533. <dt><code class="docutils literal notranslate"><span class="pre">&quot;resolve&quot;</span></code></dt><dd><p>resolve option conflicts intelligently (see below)</p>

  1534. </dd>

  1535. </dl>

  1536. </div></blockquote>

  1537. <p>As an example, let’s define an <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a> that resolves conflicts

  1538. intelligently and add conflicting options to it:</p>

  1539. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">conflict_handler</span><span class="o">=</span><span class="s2">&quot;resolve&quot;</span><span class="p">)</span>

  1540. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-n&quot;</span><span class="p">,</span> <span class="s2">&quot;--dry-run&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;do no harm&quot;</span><span class="p">)</span>

  1541. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-n&quot;</span><span class="p">,</span> <span class="s2">&quot;--noisy&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;be noisy&quot;</span><span class="p">)</span>

  1542. </pre></div>

  1543. </div>

  1544. <p>At this point, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> detects that a previously added option is already

  1545. using the <code class="docutils literal notranslate"><span class="pre">-n</span></code> option string.  Since <code class="docutils literal notranslate"><span class="pre">conflict_handler</span></code> is <code class="docutils literal notranslate"><span class="pre">&quot;resolve&quot;</span></code>,

  1546. it resolves the situation by removing <code class="docutils literal notranslate"><span class="pre">-n</span></code> from the earlier option’s list of

  1547. option strings.  Now <code class="docutils literal notranslate"><span class="pre">--dry-run</span></code> is the only way for the user to activate

  1548. that option.  If the user asks for help, the help message will reflect that:</p>

  1549. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Options</span><span class="p">:</span>

  1550.   <span class="o">--</span><span class="n">dry</span><span class="o">-</span><span class="n">run</span>     <span class="n">do</span> <span class="n">no</span> <span class="n">harm</span>

  1551.   <span class="o">...</span>

  1552.   <span class="o">-</span><span class="n">n</span><span class="p">,</span> <span class="o">--</span><span class="n">noisy</span>   <span class="n">be</span> <span class="n">noisy</span>

  1553. </pre></div>

  1554. </div>

  1555. <p>It’s possible to whittle away the option strings for a previously added option

  1556. until there are none left, and the user has no way of invoking that option from

  1557. the command-line.  In that case, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> removes that option completely,

  1558. so it doesn’t show up in help text or anywhere else. Carrying on with our

  1559. existing OptionParser:</p>

  1560. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--dry-run&quot;</span><span class="p">,</span> <span class="o">...</span><span class="p">,</span> <span class="n">help</span><span class="o">=</span><span class="s2">&quot;new dry-run option&quot;</span><span class="p">)</span>

  1561. </pre></div>

  1562. </div>

  1563. <p>At this point, the original <code class="docutils literal notranslate"><span class="pre">-n</span></code>/<code class="docutils literal notranslate"><span class="pre">--dry-run</span></code> option is no longer

  1564. accessible, so <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> removes it, leaving this help text:</p>

  1565. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">Options</span><span class="p">:</span>

  1566.   <span class="o">...</span>

  1567.   <span class="o">-</span><span class="n">n</span><span class="p">,</span> <span class="o">--</span><span class="n">noisy</span>   <span class="n">be</span> <span class="n">noisy</span>

  1568.   <span class="o">--</span><span class="n">dry</span><span class="o">-</span><span class="n">run</span>     <span class="n">new</span> <span class="n">dry</span><span class="o">-</span><span class="n">run</span> <span class="n">option</span>

  1569. </pre></div>

  1570. </div>

  1571. </section>

  1572. <section id="cleanup">

  1573. <span id="optparse-cleanup"></span><h3>Cleanup<a class="headerlink" href="#cleanup" title="Link to this heading">¶</a></h3>

  1574. <p>OptionParser instances have several cyclic references.  This should not be a

  1575. problem for Python’s garbage collector, but you may wish to break the cyclic

  1576. references explicitly by calling <code class="xref py py-meth docutils literal notranslate"><span class="pre">destroy()</span></code> on your

  1577. OptionParser once you are done with it.  This is particularly useful in

  1578. long-running applications where large object graphs are reachable from your

  1579. OptionParser.</p>

  1580. </section>

  1581. <section id="other-methods">

  1582. <span id="optparse-other-methods"></span><h3>Other methods<a class="headerlink" href="#other-methods" title="Link to this heading">¶</a></h3>

  1583. <p>OptionParser supports several other public methods:</p>

  1584. <dl class="py method">

  1585. <dt class="sig sig-object py" id="optparse.OptionParser.set_usage">

  1586. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">set_usage</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">usage</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.set_usage" title="Link to this definition">¶</a></dt>

  1587. <dd><p>Set the usage string according to the rules described above for the <code class="docutils literal notranslate"><span class="pre">usage</span></code>

  1588. constructor keyword argument.  Passing <code class="docutils literal notranslate"><span class="pre">None</span></code> sets the default usage

  1589. string; use <code class="xref py py-const docutils literal notranslate"><span class="pre">optparse.SUPPRESS_USAGE</span></code> to suppress a usage message.</p>

  1590. </dd></dl>

  1591. 

  1592. <dl class="py method">

  1593. <dt class="sig sig-object py" id="optparse.OptionParser.print_usage">

  1594. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">print_usage</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">file</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.print_usage" title="Link to this definition">¶</a></dt>

  1595. <dd><p>Print the usage message for the current program (<code class="docutils literal notranslate"><span class="pre">self.usage</span></code>) to <em>file</em>

  1596. (default stdout).  Any occurrence of the string <code class="docutils literal notranslate"><span class="pre">%prog</span></code> in <code class="docutils literal notranslate"><span class="pre">self.usage</span></code>

  1597. is replaced with the name of the current program.  Does nothing if

  1598. <code class="docutils literal notranslate"><span class="pre">self.usage</span></code> is empty or not defined.</p>

  1599. </dd></dl>

  1600. 

  1601. <dl class="py method">

  1602. <dt class="sig sig-object py" id="optparse.OptionParser.get_usage">

  1603. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">get_usage</span></span><span class="sig-paren">(</span><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.get_usage" title="Link to this definition">¶</a></dt>

  1604. <dd><p>Same as <a class="reference internal" href="#optparse.OptionParser.print_usage" title="optparse.OptionParser.print_usage"><code class="xref py py-meth docutils literal notranslate"><span class="pre">print_usage()</span></code></a> but returns the usage string instead of

  1605. printing it.</p>

  1606. </dd></dl>

  1607. 

  1608. <dl class="py method">

  1609. <dt class="sig sig-object py" id="optparse.OptionParser.set_defaults">

  1610. <span class="sig-prename descclassname"><span class="pre">OptionParser.</span></span><span class="sig-name descname"><span class="pre">set_defaults</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">dest=value</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">...</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#optparse.OptionParser.set_defaults" title="Link to this definition">¶</a></dt>

  1611. <dd><p>Set default values for several option destinations at once.  Using

  1612. <a class="reference internal" href="#optparse.OptionParser.set_defaults" title="optparse.OptionParser.set_defaults"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_defaults()</span></code></a> is the preferred way to set default values for options,

  1613. since multiple options can share the same destination.  For example, if

  1614. several “mode” options all set the same destination, any one of them can set

  1615. the default, and the last one wins:</p>

  1616. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--advanced&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span>

  1617.                   <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;mode&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="s2">&quot;advanced&quot;</span><span class="p">,</span>

  1618.                   <span class="n">default</span><span class="o">=</span><span class="s2">&quot;novice&quot;</span><span class="p">)</span>    <span class="c1"># overridden below</span>

  1619. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--novice&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span>

  1620.                   <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;mode&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="s2">&quot;novice&quot;</span><span class="p">,</span>

  1621.                   <span class="n">default</span><span class="o">=</span><span class="s2">&quot;advanced&quot;</span><span class="p">)</span>  <span class="c1"># overrides above setting</span>

  1622. </pre></div>

  1623. </div>

  1624. <p>To avoid this confusion, use <a class="reference internal" href="#optparse.OptionParser.set_defaults" title="optparse.OptionParser.set_defaults"><code class="xref py py-meth docutils literal notranslate"><span class="pre">set_defaults()</span></code></a>:</p>

  1625. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">set_defaults</span><span class="p">(</span><span class="n">mode</span><span class="o">=</span><span class="s2">&quot;advanced&quot;</span><span class="p">)</span>

  1626. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--advanced&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span>

  1627.                   <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;mode&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="s2">&quot;advanced&quot;</span><span class="p">)</span>

  1628. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--novice&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_const&quot;</span><span class="p">,</span>

  1629.                   <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;mode&quot;</span><span class="p">,</span> <span class="n">const</span><span class="o">=</span><span class="s2">&quot;novice&quot;</span><span class="p">)</span>

  1630. </pre></div>

  1631. </div>

  1632. </dd></dl>

  1633. 

  1634. </section>

  1635. </section>

  1636. <section id="option-callbacks">

  1637. <span id="optparse-option-callbacks"></span><h2>Option Callbacks<a class="headerlink" href="#option-callbacks" title="Link to this heading">¶</a></h2>

  1638. <p>When <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s built-in actions and types aren’t quite enough for your

  1639. needs, you have two choices: extend <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> or define a callback option.

  1640. Extending <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> is more general, but overkill for a lot of simple

  1641. cases.  Quite often a simple callback is all you need.</p>

  1642. <p>There are two steps to defining a callback option:</p>

  1643. <ul class="simple">

  1644. <li><p>define the option itself using the <code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code> action</p></li>

  1645. <li><p>write the callback; this is a function (or method) that takes at least four

  1646. arguments, as described below</p></li>

  1647. </ul>

  1648. <section id="defining-a-callback-option">

  1649. <span id="optparse-defining-callback-option"></span><h3>Defining a callback option<a class="headerlink" href="#defining-a-callback-option" title="Link to this heading">¶</a></h3>

  1650. <p>As always, the easiest way to define a callback option is by using the

  1651. <a class="reference internal" href="#optparse.OptionParser.add_option" title="optparse.OptionParser.add_option"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.add_option()</span></code></a> method.  Apart from <a class="reference internal" href="#optparse.Option.action" title="optparse.Option.action"><code class="xref py py-attr docutils literal notranslate"><span class="pre">action</span></code></a>, the

  1652. only option attribute you must specify is <code class="docutils literal notranslate"><span class="pre">callback</span></code>, the function to call:</p>

  1653. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-c&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">my_callback</span><span class="p">)</span>

  1654. </pre></div>

  1655. </div>

  1656. <p><code class="docutils literal notranslate"><span class="pre">callback</span></code> is a function (or other callable object), so you must have already

  1657. defined <code class="docutils literal notranslate"><span class="pre">my_callback()</span></code> when you create this callback option. In this simple

  1658. case, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> doesn’t even know if <code class="docutils literal notranslate"><span class="pre">-c</span></code> takes any arguments,

  1659. which usually means that the option takes no arguments—the mere presence of

  1660. <code class="docutils literal notranslate"><span class="pre">-c</span></code> on the command-line is all it needs to know.  In some

  1661. circumstances, though, you might want your callback to consume an arbitrary

  1662. number of command-line arguments.  This is where writing callbacks gets tricky;

  1663. it’s covered later in this section.</p>

  1664. <p><a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> always passes four particular arguments to your callback, and it

  1665. will only pass additional arguments if you specify them via

  1666. <a class="reference internal" href="#optparse.Option.callback_args" title="optparse.Option.callback_args"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_args</span></code></a> and <a class="reference internal" href="#optparse.Option.callback_kwargs" title="optparse.Option.callback_kwargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_kwargs</span></code></a>.  Thus, the

  1667. minimal callback function signature is:</p>

  1668. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">my_callback</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1669. </pre></div>

  1670. </div>

  1671. <p>The four arguments to a callback are described below.</p>

  1672. <p>There are several other option attributes that you can supply when you define a

  1673. callback option:</p>

  1674. <dl class="simple">

  1675. <dt><a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a></dt><dd><p>has its usual meaning: as with the <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code> or <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code> actions, it

  1676. instructs <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> to consume one argument and convert it to

  1677. <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>.  Rather than storing the converted value(s) anywhere,

  1678. though, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> passes it to your callback function.</p>

  1679. </dd>

  1680. <dt><a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a></dt><dd><p>also has its usual meaning: if it is supplied and &gt; 1, <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will

  1681. consume <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a> arguments, each of which must be convertible to

  1682. <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>.  It then passes a tuple of converted values to your

  1683. callback.</p>

  1684. </dd>

  1685. <dt><a class="reference internal" href="#optparse.Option.callback_args" title="optparse.Option.callback_args"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_args</span></code></a></dt><dd><p>a tuple of extra positional arguments to pass to the callback</p>

  1686. </dd>

  1687. <dt><a class="reference internal" href="#optparse.Option.callback_kwargs" title="optparse.Option.callback_kwargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_kwargs</span></code></a></dt><dd><p>a dictionary of extra keyword arguments to pass to the callback</p>

  1688. </dd>

  1689. </dl>

  1690. </section>

  1691. <section id="how-callbacks-are-called">

  1692. <span id="optparse-how-callbacks-called"></span><h3>How callbacks are called<a class="headerlink" href="#how-callbacks-are-called" title="Link to this heading">¶</a></h3>

  1693. <p>All callbacks are called as follows:</p>

  1694. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">func</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">,</span> <span class="o">*</span><span class="n">args</span><span class="p">,</span> <span class="o">**</span><span class="n">kwargs</span><span class="p">)</span>

  1695. </pre></div>

  1696. </div>

  1697. <p>where</p>

  1698. <dl>

  1699. <dt><code class="docutils literal notranslate"><span class="pre">option</span></code></dt><dd><p>is the Option instance that’s calling the callback</p>

  1700. </dd>

  1701. <dt><code class="docutils literal notranslate"><span class="pre">opt_str</span></code></dt><dd><p>is the option string seen on the command-line that’s triggering the callback.

  1702. (If an abbreviated long option was used, <code class="docutils literal notranslate"><span class="pre">opt_str</span></code> will be the full,

  1703. canonical option string—e.g. if the user puts <code class="docutils literal notranslate"><span class="pre">--foo</span></code> on the

  1704. command-line as an abbreviation for <code class="docutils literal notranslate"><span class="pre">--foobar</span></code>, then <code class="docutils literal notranslate"><span class="pre">opt_str</span></code> will be

  1705. <code class="docutils literal notranslate"><span class="pre">&quot;--foobar&quot;</span></code>.)</p>

  1706. </dd>

  1707. <dt><code class="docutils literal notranslate"><span class="pre">value</span></code></dt><dd><p>is the argument to this option seen on the command-line.  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> will

  1708. only expect an argument if <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> is set; the type of <code class="docutils literal notranslate"><span class="pre">value</span></code> will be

  1709. the type implied by the option’s type.  If <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> for this option is

  1710. <code class="docutils literal notranslate"><span class="pre">None</span></code> (no argument expected), then <code class="docutils literal notranslate"><span class="pre">value</span></code> will be <code class="docutils literal notranslate"><span class="pre">None</span></code>.  If <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>

  1711. &gt; 1, <code class="docutils literal notranslate"><span class="pre">value</span></code> will be a tuple of values of the appropriate type.</p>

  1712. </dd>

  1713. <dt><code class="docutils literal notranslate"><span class="pre">parser</span></code></dt><dd><p>is the OptionParser instance driving the whole thing, mainly useful because

  1714. you can access some other interesting data through its instance attributes:</p>

  1715. <dl class="simple">

  1716. <dt><code class="docutils literal notranslate"><span class="pre">parser.largs</span></code></dt><dd><p>the current list of leftover arguments, ie. arguments that have been

  1717. consumed but are neither options nor option arguments. Feel free to modify

  1718. <code class="docutils literal notranslate"><span class="pre">parser.largs</span></code>, e.g. by adding more arguments to it.  (This list will

  1719. become <code class="docutils literal notranslate"><span class="pre">args</span></code>, the second return value of <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">parse_args()</span></code></a>.)</p>

  1720. </dd>

  1721. <dt><code class="docutils literal notranslate"><span class="pre">parser.rargs</span></code></dt><dd><p>the current list of remaining arguments, ie. with <code class="docutils literal notranslate"><span class="pre">opt_str</span></code> and

  1722. <code class="docutils literal notranslate"><span class="pre">value</span></code> (if applicable) removed, and only the arguments following them

  1723. still there.  Feel free to modify <code class="docutils literal notranslate"><span class="pre">parser.rargs</span></code>, e.g. by consuming more

  1724. arguments.</p>

  1725. </dd>

  1726. <dt><code class="docutils literal notranslate"><span class="pre">parser.values</span></code></dt><dd><p>the object where option values are by default stored (an instance of

  1727. optparse.OptionValues).  This lets callbacks use the same mechanism as the

  1728. rest of <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> for storing option values; you don’t need to mess

  1729. around with globals or closures.  You can also access or modify the

  1730. value(s) of any options already encountered on the command-line.</p>

  1731. </dd>

  1732. </dl>

  1733. </dd>

  1734. <dt><code class="docutils literal notranslate"><span class="pre">args</span></code></dt><dd><p>is a tuple of arbitrary positional arguments supplied via the

  1735. <a class="reference internal" href="#optparse.Option.callback_args" title="optparse.Option.callback_args"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_args</span></code></a> option attribute.</p>

  1736. </dd>

  1737. <dt><code class="docutils literal notranslate"><span class="pre">kwargs</span></code></dt><dd><p>is a dictionary of arbitrary keyword arguments supplied via

  1738. <a class="reference internal" href="#optparse.Option.callback_kwargs" title="optparse.Option.callback_kwargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">callback_kwargs</span></code></a>.</p>

  1739. </dd>

  1740. </dl>

  1741. </section>

  1742. <section id="raising-errors-in-a-callback">

  1743. <span id="optparse-raising-errors-in-callback"></span><h3>Raising errors in a callback<a class="headerlink" href="#raising-errors-in-a-callback" title="Link to this heading">¶</a></h3>

  1744. <p>The callback function should raise <a class="reference internal" href="#optparse.OptionValueError" title="optparse.OptionValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionValueError</span></code></a> if there are any

  1745. problems with the option or its argument(s).  <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> catches this and

  1746. terminates the program, printing the error message you supply to stderr.  Your

  1747. message should be clear, concise, accurate, and mention the option at fault.

  1748. Otherwise, the user will have a hard time figuring out what they did wrong.</p>

  1749. </section>

  1750. <section id="callback-example-1-trivial-callback">

  1751. <span id="optparse-callback-example-1"></span><h3>Callback example 1: trivial callback<a class="headerlink" href="#callback-example-1-trivial-callback" title="Link to this heading">¶</a></h3>

  1752. <p>Here’s an example of a callback option that takes no arguments, and simply

  1753. records that the option was seen:</p>

  1754. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">record_foo_seen</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1755.     <span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="o">.</span><span class="n">saw_foo</span> <span class="o">=</span> <span class="kc">True</span>

  1756. 

  1757. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--foo&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">record_foo_seen</span><span class="p">)</span>

  1758. </pre></div>

  1759. </div>

  1760. <p>Of course, you could do that with the <code class="docutils literal notranslate"><span class="pre">&quot;store_true&quot;</span></code> action.</p>

  1761. </section>

  1762. <section id="callback-example-2-check-option-order">

  1763. <span id="optparse-callback-example-2"></span><h3>Callback example 2: check option order<a class="headerlink" href="#callback-example-2-check-option-order" title="Link to this heading">¶</a></h3>

  1764. <p>Here’s a slightly more interesting example: record the fact that <code class="docutils literal notranslate"><span class="pre">-a</span></code> is

  1765. seen, but blow up if it comes after <code class="docutils literal notranslate"><span class="pre">-b</span></code> in the command-line.</p>

  1766. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">check_order</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1767.     <span class="k">if</span> <span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="o">.</span><span class="n">b</span><span class="p">:</span>

  1768.         <span class="k">raise</span> <span class="n">OptionValueError</span><span class="p">(</span><span class="s2">&quot;can&#39;t use -a after -b&quot;</span><span class="p">)</span>

  1769.     <span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="o">.</span><span class="n">a</span> <span class="o">=</span> <span class="mi">1</span>

  1770. <span class="o">...</span>

  1771. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-a&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">check_order</span><span class="p">)</span>

  1772. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-b&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;b&quot;</span><span class="p">)</span>

  1773. </pre></div>

  1774. </div>

  1775. </section>

  1776. <section id="callback-example-3-check-option-order-generalized">

  1777. <span id="optparse-callback-example-3"></span><h3>Callback example 3: check option order (generalized)<a class="headerlink" href="#callback-example-3-check-option-order-generalized" title="Link to this heading">¶</a></h3>

  1778. <p>If you want to re-use this callback for several similar options (set a flag, but

  1779. blow up if <code class="docutils literal notranslate"><span class="pre">-b</span></code> has already been seen), it needs a bit of work: the error

  1780. message and the flag that it sets must be generalized.</p>

  1781. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">check_order</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1782.     <span class="k">if</span> <span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="o">.</span><span class="n">b</span><span class="p">:</span>

  1783.         <span class="k">raise</span> <span class="n">OptionValueError</span><span class="p">(</span><span class="s2">&quot;can&#39;t use </span><span class="si">%s</span><span class="s2"> after -b&quot;</span> <span class="o">%</span> <span class="n">opt_str</span><span class="p">)</span>

  1784.     <span class="nb">setattr</span><span class="p">(</span><span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="p">,</span> <span class="n">option</span><span class="o">.</span><span class="n">dest</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>

  1785. <span class="o">...</span>

  1786. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-a&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">check_order</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;a&#39;</span><span class="p">)</span>

  1787. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-b&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store_true&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;b&quot;</span><span class="p">)</span>

  1788. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-c&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">check_order</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s1">&#39;c&#39;</span><span class="p">)</span>

  1789. </pre></div>

  1790. </div>

  1791. </section>

  1792. <section id="callback-example-4-check-arbitrary-condition">

  1793. <span id="optparse-callback-example-4"></span><h3>Callback example 4: check arbitrary condition<a class="headerlink" href="#callback-example-4-check-arbitrary-condition" title="Link to this heading">¶</a></h3>

  1794. <p>Of course, you could put any condition in there—you’re not limited to checking

  1795. the values of already-defined options.  For example, if you have options that

  1796. should not be called when the moon is full, all you have to do is this:</p>

  1797. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">check_moon</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1798.     <span class="k">if</span> <span class="n">is_moon_full</span><span class="p">():</span>

  1799.         <span class="k">raise</span> <span class="n">OptionValueError</span><span class="p">(</span><span class="s2">&quot;</span><span class="si">%s</span><span class="s2"> option invalid when moon is full&quot;</span>

  1800.                                <span class="o">%</span> <span class="n">opt_str</span><span class="p">)</span>

  1801.     <span class="nb">setattr</span><span class="p">(</span><span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="p">,</span> <span class="n">option</span><span class="o">.</span><span class="n">dest</span><span class="p">,</span> <span class="mi">1</span><span class="p">)</span>

  1802. <span class="o">...</span>

  1803. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--foo&quot;</span><span class="p">,</span>

  1804.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">check_moon</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;foo&quot;</span><span class="p">)</span>

  1805. </pre></div>

  1806. </div>

  1807. <p>(The definition of <code class="docutils literal notranslate"><span class="pre">is_moon_full()</span></code> is left as an exercise for the reader.)</p>

  1808. </section>

  1809. <section id="callback-example-5-fixed-arguments">

  1810. <span id="optparse-callback-example-5"></span><h3>Callback example 5: fixed arguments<a class="headerlink" href="#callback-example-5-fixed-arguments" title="Link to this heading">¶</a></h3>

  1811. <p>Things get slightly more interesting when you define callback options that take

  1812. a fixed number of arguments.  Specifying that a callback option takes arguments

  1813. is similar to defining a <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code> or <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code> option: if you define

  1814. <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a>, then the option takes one argument that must be

  1815. convertible to that type; if you further define <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a>, then the

  1816. option takes <a class="reference internal" href="#optparse.Option.nargs" title="optparse.Option.nargs"><code class="xref py py-attr docutils literal notranslate"><span class="pre">nargs</span></code></a> arguments.</p>

  1817. <p>Here’s an example that just emulates the standard <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code> action:</p>

  1818. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">store_value</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1819.     <span class="nb">setattr</span><span class="p">(</span><span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="p">,</span> <span class="n">option</span><span class="o">.</span><span class="n">dest</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>

  1820. <span class="o">...</span>

  1821. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;--foo&quot;</span><span class="p">,</span>

  1822.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">store_value</span><span class="p">,</span>

  1823.                   <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;int&quot;</span><span class="p">,</span> <span class="n">nargs</span><span class="o">=</span><span class="mi">3</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;foo&quot;</span><span class="p">)</span>

  1824. </pre></div>

  1825. </div>

  1826. <p>Note that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> takes care of consuming 3 arguments and converting

  1827. them to integers for you; all you have to do is store them.  (Or whatever;

  1828. obviously you don’t need a callback for this example.)</p>

  1829. </section>

  1830. <section id="callback-example-6-variable-arguments">

  1831. <span id="optparse-callback-example-6"></span><h3>Callback example 6: variable arguments<a class="headerlink" href="#callback-example-6-variable-arguments" title="Link to this heading">¶</a></h3>

  1832. <p>Things get hairy when you want an option to take a variable number of arguments.

  1833. For this case, you must write a callback, as <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> doesn’t provide any

  1834. built-in capabilities for it.  And you have to deal with certain intricacies of

  1835. conventional Unix command-line parsing that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> normally handles for

  1836. you.  In particular, callbacks should implement the conventional rules for bare

  1837. <code class="docutils literal notranslate"><span class="pre">--</span></code> and <code class="docutils literal notranslate"><span class="pre">-</span></code> arguments:</p>

  1838. <ul class="simple">

  1839. <li><p>either <code class="docutils literal notranslate"><span class="pre">--</span></code> or <code class="docutils literal notranslate"><span class="pre">-</span></code> can be option arguments</p></li>

  1840. <li><p>bare <code class="docutils literal notranslate"><span class="pre">--</span></code> (if not the argument to some option): halt command-line

  1841. processing and discard the <code class="docutils literal notranslate"><span class="pre">--</span></code></p></li>

  1842. <li><p>bare <code class="docutils literal notranslate"><span class="pre">-</span></code> (if not the argument to some option): halt command-line

  1843. processing but keep the <code class="docutils literal notranslate"><span class="pre">-</span></code> (append it to <code class="docutils literal notranslate"><span class="pre">parser.largs</span></code>)</p></li>

  1844. </ul>

  1845. <p>If you want an option that takes a variable number of arguments, there are

  1846. several subtle, tricky issues to worry about.  The exact implementation you

  1847. choose will be based on which trade-offs you’re willing to make for your

  1848. application (which is why <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> doesn’t support this sort of thing

  1849. directly).</p>

  1850. <p>Nevertheless, here’s a stab at a callback for an option with variable

  1851. arguments:</p>

  1852. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">vararg_callback</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt_str</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  1853.     <span class="k">assert</span> <span class="n">value</span> <span class="ow">is</span> <span class="kc">None</span>

  1854.     <span class="n">value</span> <span class="o">=</span> <span class="p">[]</span>

  1855. 

  1856.     <span class="k">def</span> <span class="nf">floatable</span><span class="p">(</span><span class="nb">str</span><span class="p">):</span>

  1857.         <span class="k">try</span><span class="p">:</span>

  1858.             <span class="nb">float</span><span class="p">(</span><span class="nb">str</span><span class="p">)</span>

  1859.             <span class="k">return</span> <span class="kc">True</span>

  1860.         <span class="k">except</span> <span class="ne">ValueError</span><span class="p">:</span>

  1861.             <span class="k">return</span> <span class="kc">False</span>

  1862. 

  1863.     <span class="k">for</span> <span class="n">arg</span> <span class="ow">in</span> <span class="n">parser</span><span class="o">.</span><span class="n">rargs</span><span class="p">:</span>

  1864.         <span class="c1"># stop on --foo like options</span>

  1865.         <span class="k">if</span> <span class="n">arg</span><span class="p">[:</span><span class="mi">2</span><span class="p">]</span> <span class="o">==</span> <span class="s2">&quot;--&quot;</span> <span class="ow">and</span> <span class="nb">len</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span> <span class="o">&gt;</span> <span class="mi">2</span><span class="p">:</span>

  1866.             <span class="k">break</span>

  1867.         <span class="c1"># stop on -a, but not on -3 or -3.0</span>

  1868.         <span class="k">if</span> <span class="n">arg</span><span class="p">[:</span><span class="mi">1</span><span class="p">]</span> <span class="o">==</span> <span class="s2">&quot;-&quot;</span> <span class="ow">and</span> <span class="nb">len</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span> <span class="o">&gt;</span> <span class="mi">1</span> <span class="ow">and</span> <span class="ow">not</span> <span class="n">floatable</span><span class="p">(</span><span class="n">arg</span><span class="p">):</span>

  1869.             <span class="k">break</span>

  1870.         <span class="n">value</span><span class="o">.</span><span class="n">append</span><span class="p">(</span><span class="n">arg</span><span class="p">)</span>

  1871. 

  1872.     <span class="k">del</span> <span class="n">parser</span><span class="o">.</span><span class="n">rargs</span><span class="p">[:</span><span class="nb">len</span><span class="p">(</span><span class="n">value</span><span class="p">)]</span>

  1873.     <span class="nb">setattr</span><span class="p">(</span><span class="n">parser</span><span class="o">.</span><span class="n">values</span><span class="p">,</span> <span class="n">option</span><span class="o">.</span><span class="n">dest</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>

  1874. 

  1875. <span class="o">...</span>

  1876. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-c&quot;</span><span class="p">,</span> <span class="s2">&quot;--callback&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;vararg_attr&quot;</span><span class="p">,</span>

  1877.                   <span class="n">action</span><span class="o">=</span><span class="s2">&quot;callback&quot;</span><span class="p">,</span> <span class="n">callback</span><span class="o">=</span><span class="n">vararg_callback</span><span class="p">)</span>

  1878. </pre></div>

  1879. </div>

  1880. </section>

  1881. </section>

  1882. <section id="extending-optparse">

  1883. <span id="optparse-extending-optparse"></span><h2>Extending <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a><a class="headerlink" href="#extending-optparse" title="Link to this heading">¶</a></h2>

  1884. <p>Since the two major controlling factors in how <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> interprets

  1885. command-line options are the action and type of each option, the most likely

  1886. direction of extension is to add new actions and new types.</p>

  1887. <section id="adding-new-types">

  1888. <span id="optparse-adding-new-types"></span><h3>Adding new types<a class="headerlink" href="#adding-new-types" title="Link to this heading">¶</a></h3>

  1889. <p>To add new types, you need to define your own subclass of <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s

  1890. <a class="reference internal" href="#optparse.Option" title="optparse.Option"><code class="xref py py-class docutils literal notranslate"><span class="pre">Option</span></code></a> class.  This class has a couple of attributes that define

  1891. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s types: <a class="reference internal" href="#optparse.Option.TYPES" title="optparse.Option.TYPES"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPES</span></code></a> and <a class="reference internal" href="#optparse.Option.TYPE_CHECKER" title="optparse.Option.TYPE_CHECKER"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPE_CHECKER</span></code></a>.</p>

  1892. <dl class="py attribute">

  1893. <dt class="sig sig-object py" id="optparse.Option.TYPES">

  1894. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">TYPES</span></span><a class="headerlink" href="#optparse.Option.TYPES" title="Link to this definition">¶</a></dt>

  1895. <dd><p>A tuple of type names; in your subclass, simply define a new tuple

  1896. <a class="reference internal" href="#optparse.Option.TYPES" title="optparse.Option.TYPES"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPES</span></code></a> that builds on the standard one.</p>

  1897. </dd></dl>

  1898. 

  1899. <dl class="py attribute">

  1900. <dt class="sig sig-object py" id="optparse.Option.TYPE_CHECKER">

  1901. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">TYPE_CHECKER</span></span><a class="headerlink" href="#optparse.Option.TYPE_CHECKER" title="Link to this definition">¶</a></dt>

  1902. <dd><p>A dictionary mapping type names to type-checking functions.  A type-checking

  1903. function has the following signature:</p>

  1904. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">check_mytype</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>

  1905. </pre></div>

  1906. </div>

  1907. <p>where <code class="docutils literal notranslate"><span class="pre">option</span></code> is an <a class="reference internal" href="#optparse.Option" title="optparse.Option"><code class="xref py py-class docutils literal notranslate"><span class="pre">Option</span></code></a> instance, <code class="docutils literal notranslate"><span class="pre">opt</span></code> is an option string

  1908. (e.g., <code class="docutils literal notranslate"><span class="pre">-f</span></code>), and <code class="docutils literal notranslate"><span class="pre">value</span></code> is the string from the command line that must

  1909. be checked and converted to your desired type.  <code class="docutils literal notranslate"><span class="pre">check_mytype()</span></code> should

  1910. return an object of the hypothetical type <code class="docutils literal notranslate"><span class="pre">mytype</span></code>.  The value returned by

  1911. a type-checking function will wind up in the OptionValues instance returned

  1912. by <a class="reference internal" href="#optparse.OptionParser.parse_args" title="optparse.OptionParser.parse_args"><code class="xref py py-meth docutils literal notranslate"><span class="pre">OptionParser.parse_args()</span></code></a>, or be passed to a callback as the

  1913. <code class="docutils literal notranslate"><span class="pre">value</span></code> parameter.</p>

  1914. <p>Your type-checking function should raise <a class="reference internal" href="#optparse.OptionValueError" title="optparse.OptionValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionValueError</span></code></a> if it

  1915. encounters any problems.  <a class="reference internal" href="#optparse.OptionValueError" title="optparse.OptionValueError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">OptionValueError</span></code></a> takes a single string

  1916. argument, which is passed as-is to <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>’s <code class="xref py py-meth docutils literal notranslate"><span class="pre">error()</span></code>

  1917. method, which in turn prepends the program name and the string <code class="docutils literal notranslate"><span class="pre">&quot;error:&quot;</span></code>

  1918. and prints everything to stderr before terminating the process.</p>

  1919. </dd></dl>

  1920. 

  1921. <p>Here’s a silly example that demonstrates adding a <code class="docutils literal notranslate"><span class="pre">&quot;complex&quot;</span></code> option type to

  1922. parse Python-style complex numbers on the command line.  (This is even sillier

  1923. than it used to be, because <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> 1.3 added built-in support for

  1924. complex numbers, but never mind.)</p>

  1925. <p>First, the necessary imports:</p>

  1926. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">copy</span> <span class="kn">import</span> <span class="n">copy</span>

  1927. <span class="kn">from</span> <span class="nn">optparse</span> <span class="kn">import</span> <span class="n">Option</span><span class="p">,</span> <span class="n">OptionValueError</span>

  1928. </pre></div>

  1929. </div>

  1930. <p>You need to define your type-checker first, since it’s referred to later (in the

  1931. <a class="reference internal" href="#optparse.Option.TYPE_CHECKER" title="optparse.Option.TYPE_CHECKER"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPE_CHECKER</span></code></a> class attribute of your Option subclass):</p>

  1932. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">check_complex</span><span class="p">(</span><span class="n">option</span><span class="p">,</span> <span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">):</span>

  1933.     <span class="k">try</span><span class="p">:</span>

  1934.         <span class="k">return</span> <span class="nb">complex</span><span class="p">(</span><span class="n">value</span><span class="p">)</span>

  1935.     <span class="k">except</span> <span class="ne">ValueError</span><span class="p">:</span>

  1936.         <span class="k">raise</span> <span class="n">OptionValueError</span><span class="p">(</span>

  1937.             <span class="s2">&quot;option </span><span class="si">%s</span><span class="s2">: invalid complex value: </span><span class="si">%r</span><span class="s2">&quot;</span> <span class="o">%</span> <span class="p">(</span><span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">))</span>

  1938. </pre></div>

  1939. </div>

  1940. <p>Finally, the Option subclass:</p>

  1941. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">MyOption</span> <span class="p">(</span><span class="n">Option</span><span class="p">):</span>

  1942.     <span class="n">TYPES</span> <span class="o">=</span> <span class="n">Option</span><span class="o">.</span><span class="n">TYPES</span> <span class="o">+</span> <span class="p">(</span><span class="s2">&quot;complex&quot;</span><span class="p">,)</span>

  1943.     <span class="n">TYPE_CHECKER</span> <span class="o">=</span> <span class="n">copy</span><span class="p">(</span><span class="n">Option</span><span class="o">.</span><span class="n">TYPE_CHECKER</span><span class="p">)</span>

  1944.     <span class="n">TYPE_CHECKER</span><span class="p">[</span><span class="s2">&quot;complex&quot;</span><span class="p">]</span> <span class="o">=</span> <span class="n">check_complex</span>

  1945. </pre></div>

  1946. </div>

  1947. <p>(If we didn’t make a <a class="reference internal" href="copy.html#module-copy" title="copy: Shallow and deep copy operations."><code class="xref py py-func docutils literal notranslate"><span class="pre">copy()</span></code></a> of <a class="reference internal" href="#optparse.Option.TYPE_CHECKER" title="optparse.Option.TYPE_CHECKER"><code class="xref py py-attr docutils literal notranslate"><span class="pre">Option.TYPE_CHECKER</span></code></a>, we would end

  1948. up modifying the <a class="reference internal" href="#optparse.Option.TYPE_CHECKER" title="optparse.Option.TYPE_CHECKER"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPE_CHECKER</span></code></a> attribute of <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>’s

  1949. Option class.  This being Python, nothing stops you from doing that except good

  1950. manners and common sense.)</p>

  1951. <p>That’s it!  Now you can write a script that uses the new option type just like

  1952. any other <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>-based script, except you have to instruct your

  1953. OptionParser to use MyOption instead of Option:</p>

  1954. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">option_class</span><span class="o">=</span><span class="n">MyOption</span><span class="p">)</span>

  1955. <span class="n">parser</span><span class="o">.</span><span class="n">add_option</span><span class="p">(</span><span class="s2">&quot;-c&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;complex&quot;</span><span class="p">)</span>

  1956. </pre></div>

  1957. </div>

  1958. <p>Alternately, you can build your own option list and pass it to OptionParser; if

  1959. you don’t use <code class="xref py py-meth docutils literal notranslate"><span class="pre">add_option()</span></code> in the above way, you don’t need to tell

  1960. OptionParser which option class to use:</p>

  1961. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">option_list</span> <span class="o">=</span> <span class="p">[</span><span class="n">MyOption</span><span class="p">(</span><span class="s2">&quot;-c&quot;</span><span class="p">,</span> <span class="n">action</span><span class="o">=</span><span class="s2">&quot;store&quot;</span><span class="p">,</span> <span class="nb">type</span><span class="o">=</span><span class="s2">&quot;complex&quot;</span><span class="p">,</span> <span class="n">dest</span><span class="o">=</span><span class="s2">&quot;c&quot;</span><span class="p">)]</span>

  1962. <span class="n">parser</span> <span class="o">=</span> <span class="n">OptionParser</span><span class="p">(</span><span class="n">option_list</span><span class="o">=</span><span class="n">option_list</span><span class="p">)</span>

  1963. </pre></div>

  1964. </div>

  1965. </section>

  1966. <section id="adding-new-actions">

  1967. <span id="optparse-adding-new-actions"></span><h3>Adding new actions<a class="headerlink" href="#adding-new-actions" title="Link to this heading">¶</a></h3>

  1968. <p>Adding new actions is a bit trickier, because you have to understand that

  1969. <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> has a couple of classifications for actions:</p>

  1970. <dl class="simple">

  1971. <dt>“store” actions</dt><dd><p>actions that result in <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> storing a value to an attribute of the

  1972. current OptionValues instance; these options require a <a class="reference internal" href="#optparse.Option.dest" title="optparse.Option.dest"><code class="xref py py-attr docutils literal notranslate"><span class="pre">dest</span></code></a>

  1973. attribute to be supplied to the Option constructor.</p>

  1974. </dd>

  1975. <dt>“typed” actions</dt><dd><p>actions that take a value from the command line and expect it to be of a

  1976. certain type; or rather, a string that can be converted to a certain type.

  1977. These options require a <a class="reference internal" href="#optparse.Option.type" title="optparse.Option.type"><code class="xref py py-attr docutils literal notranslate"><span class="pre">type</span></code></a> attribute to the Option

  1978. constructor.</p>

  1979. </dd>

  1980. </dl>

  1981. <p>These are overlapping sets: some default “store” actions are <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code>,

  1982. <code class="docutils literal notranslate"><span class="pre">&quot;store_const&quot;</span></code>, <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code>, and <code class="docutils literal notranslate"><span class="pre">&quot;count&quot;</span></code>, while the default “typed”

  1983. actions are <code class="docutils literal notranslate"><span class="pre">&quot;store&quot;</span></code>, <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code>, and <code class="docutils literal notranslate"><span class="pre">&quot;callback&quot;</span></code>.</p>

  1984. <p>When you add an action, you need to categorize it by listing it in at least one

  1985. of the following class attributes of Option (all are lists of strings):</p>

  1986. <dl class="py attribute">

  1987. <dt class="sig sig-object py" id="optparse.Option.ACTIONS">

  1988. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">ACTIONS</span></span><a class="headerlink" href="#optparse.Option.ACTIONS" title="Link to this definition">¶</a></dt>

  1989. <dd><p>All actions must be listed in ACTIONS.</p>

  1990. </dd></dl>

  1991. 

  1992. <dl class="py attribute">

  1993. <dt class="sig sig-object py" id="optparse.Option.STORE_ACTIONS">

  1994. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">STORE_ACTIONS</span></span><a class="headerlink" href="#optparse.Option.STORE_ACTIONS" title="Link to this definition">¶</a></dt>

  1995. <dd><p>“store” actions are additionally listed here.</p>

  1996. </dd></dl>

  1997. 

  1998. <dl class="py attribute">

  1999. <dt class="sig sig-object py" id="optparse.Option.TYPED_ACTIONS">

  2000. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">TYPED_ACTIONS</span></span><a class="headerlink" href="#optparse.Option.TYPED_ACTIONS" title="Link to this definition">¶</a></dt>

  2001. <dd><p>“typed” actions are additionally listed here.</p>

  2002. </dd></dl>

  2003. 

  2004. <dl class="py attribute">

  2005. <dt class="sig sig-object py" id="optparse.Option.ALWAYS_TYPED_ACTIONS">

  2006. <span class="sig-prename descclassname"><span class="pre">Option.</span></span><span class="sig-name descname"><span class="pre">ALWAYS_TYPED_ACTIONS</span></span><a class="headerlink" href="#optparse.Option.ALWAYS_TYPED_ACTIONS" title="Link to this definition">¶</a></dt>

  2007. <dd><p>Actions that always take a type (i.e. whose options always take a value) are

  2008. additionally listed here.  The only effect of this is that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  2009. assigns the default type, <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code>, to options with no explicit type

  2010. whose action is listed in <a class="reference internal" href="#optparse.Option.ALWAYS_TYPED_ACTIONS" title="optparse.Option.ALWAYS_TYPED_ACTIONS"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ALWAYS_TYPED_ACTIONS</span></code></a>.</p>

  2011. </dd></dl>

  2012. 

  2013. <p>In order to actually implement your new action, you must override Option’s

  2014. <code class="xref py py-meth docutils literal notranslate"><span class="pre">take_action()</span></code> method and add a case that recognizes your action.</p>

  2015. <p>For example, let’s add an <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> action.  This is similar to the standard

  2016. <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code> action, but instead of taking a single value from the command-line

  2017. and appending it to an existing list, <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> will take multiple values in

  2018. a single comma-delimited string, and extend an existing list with them.  That

  2019. is, if <code class="docutils literal notranslate"><span class="pre">--names</span></code> is an <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> option of type <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code>, the command

  2020. line</p>

  2021. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="o">--</span><span class="n">names</span><span class="o">=</span><span class="n">foo</span><span class="p">,</span><span class="n">bar</span> <span class="o">--</span><span class="n">names</span> <span class="n">blah</span> <span class="o">--</span><span class="n">names</span> <span class="n">ding</span><span class="p">,</span><span class="n">dong</span>

  2022. </pre></div>

  2023. </div>

  2024. <p>would result in a list</p>

  2025. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">[</span><span class="s2">&quot;foo&quot;</span><span class="p">,</span> <span class="s2">&quot;bar&quot;</span><span class="p">,</span> <span class="s2">&quot;blah&quot;</span><span class="p">,</span> <span class="s2">&quot;ding&quot;</span><span class="p">,</span> <span class="s2">&quot;dong&quot;</span><span class="p">]</span>

  2026. </pre></div>

  2027. </div>

  2028. <p>Again we define a subclass of Option:</p>

  2029. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">class</span> <span class="nc">MyOption</span><span class="p">(</span><span class="n">Option</span><span class="p">):</span>

  2030. 

  2031.     <span class="n">ACTIONS</span> <span class="o">=</span> <span class="n">Option</span><span class="o">.</span><span class="n">ACTIONS</span> <span class="o">+</span> <span class="p">(</span><span class="s2">&quot;extend&quot;</span><span class="p">,)</span>

  2032.     <span class="n">STORE_ACTIONS</span> <span class="o">=</span> <span class="n">Option</span><span class="o">.</span><span class="n">STORE_ACTIONS</span> <span class="o">+</span> <span class="p">(</span><span class="s2">&quot;extend&quot;</span><span class="p">,)</span>

  2033.     <span class="n">TYPED_ACTIONS</span> <span class="o">=</span> <span class="n">Option</span><span class="o">.</span><span class="n">TYPED_ACTIONS</span> <span class="o">+</span> <span class="p">(</span><span class="s2">&quot;extend&quot;</span><span class="p">,)</span>

  2034.     <span class="n">ALWAYS_TYPED_ACTIONS</span> <span class="o">=</span> <span class="n">Option</span><span class="o">.</span><span class="n">ALWAYS_TYPED_ACTIONS</span> <span class="o">+</span> <span class="p">(</span><span class="s2">&quot;extend&quot;</span><span class="p">,)</span>

  2035. 

  2036.     <span class="k">def</span> <span class="nf">take_action</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">action</span><span class="p">,</span> <span class="n">dest</span><span class="p">,</span> <span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">values</span><span class="p">,</span> <span class="n">parser</span><span class="p">):</span>

  2037.         <span class="k">if</span> <span class="n">action</span> <span class="o">==</span> <span class="s2">&quot;extend&quot;</span><span class="p">:</span>

  2038.             <span class="n">lvalue</span> <span class="o">=</span> <span class="n">value</span><span class="o">.</span><span class="n">split</span><span class="p">(</span><span class="s2">&quot;,&quot;</span><span class="p">)</span>

  2039.             <span class="n">values</span><span class="o">.</span><span class="n">ensure_value</span><span class="p">(</span><span class="n">dest</span><span class="p">,</span> <span class="p">[])</span><span class="o">.</span><span class="n">extend</span><span class="p">(</span><span class="n">lvalue</span><span class="p">)</span>

  2040.         <span class="k">else</span><span class="p">:</span>

  2041.             <span class="n">Option</span><span class="o">.</span><span class="n">take_action</span><span class="p">(</span>

  2042.                 <span class="bp">self</span><span class="p">,</span> <span class="n">action</span><span class="p">,</span> <span class="n">dest</span><span class="p">,</span> <span class="n">opt</span><span class="p">,</span> <span class="n">value</span><span class="p">,</span> <span class="n">values</span><span class="p">,</span> <span class="n">parser</span><span class="p">)</span>

  2043. </pre></div>

  2044. </div>

  2045. <p>Features of note:</p>

  2046. <ul>

  2047. <li><p><code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> both expects a value on the command-line and stores that value

  2048. somewhere, so it goes in both <a class="reference internal" href="#optparse.Option.STORE_ACTIONS" title="optparse.Option.STORE_ACTIONS"><code class="xref py py-attr docutils literal notranslate"><span class="pre">STORE_ACTIONS</span></code></a> and

  2049. <a class="reference internal" href="#optparse.Option.TYPED_ACTIONS" title="optparse.Option.TYPED_ACTIONS"><code class="xref py py-attr docutils literal notranslate"><span class="pre">TYPED_ACTIONS</span></code></a>.</p></li>

  2050. <li><p>to ensure that <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a> assigns the default type of <code class="docutils literal notranslate"><span class="pre">&quot;string&quot;</span></code> to

  2051. <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> actions, we put the <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code> action in

  2052. <a class="reference internal" href="#optparse.Option.ALWAYS_TYPED_ACTIONS" title="optparse.Option.ALWAYS_TYPED_ACTIONS"><code class="xref py py-attr docutils literal notranslate"><span class="pre">ALWAYS_TYPED_ACTIONS</span></code></a> as well.</p></li>

  2053. <li><p><code class="xref py py-meth docutils literal notranslate"><span class="pre">MyOption.take_action()</span></code> implements just this one new action, and passes

  2054. control back to <code class="xref py py-meth docutils literal notranslate"><span class="pre">Option.take_action()</span></code> for the standard <a class="reference internal" href="#module-optparse" title="optparse: Command-line option parsing library. (deprecated)"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a>

  2055. actions.</p></li>

  2056. <li><p><code class="docutils literal notranslate"><span class="pre">values</span></code> is an instance of the optparse_parser.Values class, which provides

  2057. the very useful <code class="xref py py-meth docutils literal notranslate"><span class="pre">ensure_value()</span></code> method. <code class="xref py py-meth docutils literal notranslate"><span class="pre">ensure_value()</span></code> is

  2058. essentially <a class="reference internal" href="functions.html#getattr" title="getattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">getattr()</span></code></a> with a safety valve; it is called as</p>

  2059. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">values</span><span class="o">.</span><span class="n">ensure_value</span><span class="p">(</span><span class="n">attr</span><span class="p">,</span> <span class="n">value</span><span class="p">)</span>

  2060. </pre></div>

  2061. </div>

  2062. <p>If the <code class="docutils literal notranslate"><span class="pre">attr</span></code> attribute of <code class="docutils literal notranslate"><span class="pre">values</span></code> doesn’t exist or is <code class="docutils literal notranslate"><span class="pre">None</span></code>, then

  2063. ensure_value() first sets it to <code class="docutils literal notranslate"><span class="pre">value</span></code>, and then returns <code class="docutils literal notranslate"><span class="pre">value</span></code>. This is

  2064. very handy for actions like <code class="docutils literal notranslate"><span class="pre">&quot;extend&quot;</span></code>, <code class="docutils literal notranslate"><span class="pre">&quot;append&quot;</span></code>, and <code class="docutils literal notranslate"><span class="pre">&quot;count&quot;</span></code>, all

  2065. of which accumulate data in a variable and expect that variable to be of a

  2066. certain type (a list for the first two, an integer for the latter).  Using

  2067. <code class="xref py py-meth docutils literal notranslate"><span class="pre">ensure_value()</span></code> means that scripts using your action don’t have to worry

  2068. about setting a default value for the option destinations in question; they

  2069. can just leave the default as <code class="docutils literal notranslate"><span class="pre">None</span></code> and <code class="xref py py-meth docutils literal notranslate"><span class="pre">ensure_value()</span></code> will take care of

  2070. getting it right when it’s needed.</p>

  2071. </li>

  2072. </ul>

  2073. </section>

  2074. </section>

  2075. <section id="exceptions">

  2076. <h2>Exceptions<a class="headerlink" href="#exceptions" title="Link to this heading">¶</a></h2>

  2077. <dl class="py exception">

  2078. <dt class="sig sig-object py" id="optparse.OptionError">

  2079. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">OptionError</span></span><a class="headerlink" href="#optparse.OptionError" title="Link to this definition">¶</a></dt>

  2080. <dd><p>Raised if an <a class="reference internal" href="#optparse.Option" title="optparse.Option"><code class="xref py py-class docutils literal notranslate"><span class="pre">Option</span></code></a> instance is created with invalid or

  2081. inconsistent arguments.</p>

  2082. </dd></dl>

  2083. 

  2084. <dl class="py exception">

  2085. <dt class="sig sig-object py" id="optparse.OptionConflictError">

  2086. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">OptionConflictError</span></span><a class="headerlink" href="#optparse.OptionConflictError" title="Link to this definition">¶</a></dt>

  2087. <dd><p>Raised if conflicting options are added to an <a class="reference internal" href="#optparse.OptionParser" title="optparse.OptionParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">OptionParser</span></code></a>.</p>

  2088. </dd></dl>

  2089. 

  2090. <dl class="py exception">

  2091. <dt class="sig sig-object py" id="optparse.OptionValueError">

  2092. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">OptionValueError</span></span><a class="headerlink" href="#optparse.OptionValueError" title="Link to this definition">¶</a></dt>

  2093. <dd><p>Raised if an invalid option value is encountered on the command line.</p>

  2094. </dd></dl>

  2095. 

  2096. <dl class="py exception">

  2097. <dt class="sig sig-object py" id="optparse.BadOptionError">

  2098. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">BadOptionError</span></span><a class="headerlink" href="#optparse.BadOptionError" title="Link to this definition">¶</a></dt>

  2099. <dd><p>Raised if an invalid option is passed on the command line.</p>

  2100. </dd></dl>

  2101. 

  2102. <dl class="py exception">

  2103. <dt class="sig sig-object py" id="optparse.AmbiguousOptionError">

  2104. <em class="property"><span class="pre">exception</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">optparse.</span></span><span class="sig-name descname"><span class="pre">AmbiguousOptionError</span></span><a class="headerlink" href="#optparse.AmbiguousOptionError" title="Link to this definition">¶</a></dt>

  2105. <dd><p>Raised if an ambiguous option is passed on the command line.</p>

  2106. </dd></dl>

  2107. 

  2108. </section>

  2109. </section>

  2110. 

  2111. 

  2112.             <div class="clearer"></div>

  2113.           </div>

  2114.         </div>

  2115.       </div>

  2116.       <div class="sphinxsidebar" role="navigation" aria-label="main navigation">

  2117.         <div class="sphinxsidebarwrapper">

  2118.   <div>

  2119.     <h3><a href="../contents.html">Table of Contents</a></h3>

  2120.     <ul>

  2121. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code> — Parser for command line options</a><ul>

  2122. <li><a class="reference internal" href="#background">Background</a><ul>

  2123. <li><a class="reference internal" href="#terminology">Terminology</a></li>

  2124. <li><a class="reference internal" href="#what-are-options-for">What are options for?</a></li>

  2125. <li><a class="reference internal" href="#what-are-positional-arguments-for">What are positional arguments for?</a></li>

  2126. </ul>

  2127. </li>

  2128. <li><a class="reference internal" href="#tutorial">Tutorial</a><ul>

  2129. <li><a class="reference internal" href="#understanding-option-actions">Understanding option actions</a></li>

  2130. <li><a class="reference internal" href="#the-store-action">The store action</a></li>

  2131. <li><a class="reference internal" href="#handling-boolean-flag-options">Handling boolean (flag) options</a></li>

  2132. <li><a class="reference internal" href="#other-actions">Other actions</a></li>

  2133. <li><a class="reference internal" href="#default-values">Default values</a></li>

  2134. <li><a class="reference internal" href="#generating-help">Generating help</a><ul>

  2135. <li><a class="reference internal" href="#grouping-options">Grouping Options</a></li>

  2136. </ul>

  2137. </li>

  2138. <li><a class="reference internal" href="#printing-a-version-string">Printing a version string</a></li>

  2139. <li><a class="reference internal" href="#how-optparse-handles-errors">How <code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code> handles errors</a></li>

  2140. <li><a class="reference internal" href="#putting-it-all-together">Putting it all together</a></li>

  2141. </ul>

  2142. </li>

  2143. <li><a class="reference internal" href="#reference-guide">Reference Guide</a><ul>

  2144. <li><a class="reference internal" href="#creating-the-parser">Creating the parser</a></li>

  2145. <li><a class="reference internal" href="#populating-the-parser">Populating the parser</a></li>

  2146. <li><a class="reference internal" href="#defining-options">Defining options</a></li>

  2147. <li><a class="reference internal" href="#option-attributes">Option attributes</a></li>

  2148. <li><a class="reference internal" href="#standard-option-actions">Standard option actions</a></li>

  2149. <li><a class="reference internal" href="#standard-option-types">Standard option types</a></li>

  2150. <li><a class="reference internal" href="#parsing-arguments">Parsing arguments</a></li>

  2151. <li><a class="reference internal" href="#querying-and-manipulating-your-option-parser">Querying and manipulating your option parser</a></li>

  2152. <li><a class="reference internal" href="#conflicts-between-options">Conflicts between options</a></li>

  2153. <li><a class="reference internal" href="#cleanup">Cleanup</a></li>

  2154. <li><a class="reference internal" href="#other-methods">Other methods</a></li>

  2155. </ul>

  2156. </li>

  2157. <li><a class="reference internal" href="#option-callbacks">Option Callbacks</a><ul>

  2158. <li><a class="reference internal" href="#defining-a-callback-option">Defining a callback option</a></li>

  2159. <li><a class="reference internal" href="#how-callbacks-are-called">How callbacks are called</a></li>

  2160. <li><a class="reference internal" href="#raising-errors-in-a-callback">Raising errors in a callback</a></li>

  2161. <li><a class="reference internal" href="#callback-example-1-trivial-callback">Callback example 1: trivial callback</a></li>

  2162. <li><a class="reference internal" href="#callback-example-2-check-option-order">Callback example 2: check option order</a></li>

  2163. <li><a class="reference internal" href="#callback-example-3-check-option-order-generalized">Callback example 3: check option order (generalized)</a></li>

  2164. <li><a class="reference internal" href="#callback-example-4-check-arbitrary-condition">Callback example 4: check arbitrary condition</a></li>

  2165. <li><a class="reference internal" href="#callback-example-5-fixed-arguments">Callback example 5: fixed arguments</a></li>

  2166. <li><a class="reference internal" href="#callback-example-6-variable-arguments">Callback example 6: variable arguments</a></li>

  2167. </ul>

  2168. </li>

  2169. <li><a class="reference internal" href="#extending-optparse">Extending <code class="xref py py-mod docutils literal notranslate"><span class="pre">optparse</span></code></a><ul>

  2170. <li><a class="reference internal" href="#adding-new-types">Adding new types</a></li>

  2171. <li><a class="reference internal" href="#adding-new-actions">Adding new actions</a></li>

  2172. </ul>

  2173. </li>

  2174. <li><a class="reference internal" href="#exceptions">Exceptions</a></li>

  2175. </ul>

  2176. </li>

  2177. </ul>

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