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  195.   <section id="module-timeit">

  196. <span id="timeit-measure-execution-time-of-small-code-snippets"></span><h1><a class="reference internal" href="#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code></a> — Measure execution time of small code snippets<a class="headerlink" href="#module-timeit" title="Link to this heading">¶</a></h1>

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

  198. <hr class="docutils" id="index-0" />

  199. <p>This module provides a simple way to time small bits of Python code. It has both

  200. a <a class="reference internal" href="#timeit-command-line-interface"><span class="std std-ref">Command-Line Interface</span></a> as well as a <a class="reference internal" href="#python-interface"><span class="std std-ref">callable</span></a>

  201. one.  It avoids a number of common traps for measuring execution times.

  202. See also Tim Peters’ introduction to the “Algorithms” chapter in the second

  203. edition of <em>Python Cookbook</em>, published by O’Reilly.</p>

  204. <section id="basic-examples">

  205. <h2>Basic Examples<a class="headerlink" href="#basic-examples" title="Link to this heading">¶</a></h2>

  206. <p>The following example shows how the <a class="reference internal" href="#timeit-command-line-interface"><span class="std std-ref">Command-Line Interface</span></a>

  207. can be used to compare three different expressions:</p>

  208. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;&#39;-&#39;.join(str(n) for n in range(100))&quot;</span>

  209. <span class="go">10000 loops, best of 5: 30.2 usec per loop</span>

  210. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;&#39;-&#39;.join([str(n) for n in range(100)])&quot;</span>

  211. <span class="go">10000 loops, best of 5: 27.5 usec per loop</span>

  212. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;&#39;-&#39;.join(map(str, range(100)))&quot;</span>

  213. <span class="go">10000 loops, best of 5: 23.2 usec per loop</span>

  214. </pre></div>

  215. </div>

  216. <p>This can be achieved from the <a class="reference internal" href="#python-interface"><span class="std std-ref">Python Interface</span></a> with:</p>

  217. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">timeit</span>

  218. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;&quot;-&quot;.join(str(n) for n in range(100))&#39;</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">10000</span><span class="p">)</span>

  219. <span class="go">0.3018611848820001</span>

  220. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;&quot;-&quot;.join([str(n) for n in range(100)])&#39;</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">10000</span><span class="p">)</span>

  221. <span class="go">0.2727368790656328</span>

  222. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;&quot;-&quot;.join(map(str, range(100)))&#39;</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">10000</span><span class="p">)</span>

  223. <span class="go">0.23702679807320237</span>

  224. </pre></div>

  225. </div>

  226. <p>A callable can also be passed from the <a class="reference internal" href="#python-interface"><span class="std std-ref">Python Interface</span></a>:</p>

  227. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="k">lambda</span><span class="p">:</span> <span class="s2">&quot;-&quot;</span><span class="o">.</span><span class="n">join</span><span class="p">(</span><span class="nb">map</span><span class="p">(</span><span class="nb">str</span><span class="p">,</span> <span class="nb">range</span><span class="p">(</span><span class="mi">100</span><span class="p">))),</span> <span class="n">number</span><span class="o">=</span><span class="mi">10000</span><span class="p">)</span>

  228. <span class="go">0.19665591977536678</span>

  229. </pre></div>

  230. </div>

  231. <p>Note however that <a class="reference internal" href="#timeit.timeit" title="timeit.timeit"><code class="xref py py-func docutils literal notranslate"><span class="pre">timeit()</span></code></a> will automatically determine the number of

  232. repetitions only when the command-line interface is used.  In the

  233. <a class="reference internal" href="#timeit-examples"><span class="std std-ref">Examples</span></a> section you can find more advanced examples.</p>

  234. </section>

  235. <section id="python-interface">

  236. <span id="id1"></span><h2>Python Interface<a class="headerlink" href="#python-interface" title="Link to this heading">¶</a></h2>

  237. <p>The module defines three convenience functions and a public class:</p>

  238. <dl class="py function">

  239. <dt class="sig sig-object py" id="timeit.timeit">

  240. <span class="sig-prename descclassname"><span class="pre">timeit.</span></span><span class="sig-name descname"><span class="pre">timeit</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">stmt='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">setup='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timer=&lt;default</span> <span class="pre">timer&gt;</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">number=1000000</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">globals=None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#timeit.timeit" title="Link to this definition">¶</a></dt>

  241. <dd><p>Create a <a class="reference internal" href="#timeit.Timer" title="timeit.Timer"><code class="xref py py-class docutils literal notranslate"><span class="pre">Timer</span></code></a> instance with the given statement, <em>setup</em> code and

  242. <em>timer</em> function and run its <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> method with <em>number</em> executions.

  243. The optional <em>globals</em> argument specifies a namespace in which to execute the

  244. code.</p>

  245. <div class="versionchanged">

  246. <p><span class="versionmodified changed">Changed in version 3.5: </span>The optional <em>globals</em> parameter was added.</p>

  247. </div>

  248. </dd></dl>

  249. 

  250. <dl class="py function">

  251. <dt class="sig sig-object py" id="timeit.repeat">

  252. <span class="sig-prename descclassname"><span class="pre">timeit.</span></span><span class="sig-name descname"><span class="pre">repeat</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">stmt='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">setup='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timer=&lt;default</span> <span class="pre">timer&gt;</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">repeat=5</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">number=1000000</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">globals=None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#timeit.repeat" title="Link to this definition">¶</a></dt>

  253. <dd><p>Create a <a class="reference internal" href="#timeit.Timer" title="timeit.Timer"><code class="xref py py-class docutils literal notranslate"><span class="pre">Timer</span></code></a> instance with the given statement, <em>setup</em> code and

  254. <em>timer</em> function and run its <a class="reference internal" href="#timeit.Timer.repeat" title="timeit.Timer.repeat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">repeat()</span></code></a> method with the given <em>repeat</em>

  255. count and <em>number</em> executions.  The optional <em>globals</em> argument specifies a

  256. namespace in which to execute the code.</p>

  257. <div class="versionchanged">

  258. <p><span class="versionmodified changed">Changed in version 3.5: </span>The optional <em>globals</em> parameter was added.</p>

  259. </div>

  260. <div class="versionchanged">

  261. <p><span class="versionmodified changed">Changed in version 3.7: </span>Default value of <em>repeat</em> changed from 3 to 5.</p>

  262. </div>

  263. </dd></dl>

  264. 

  265. <dl class="py function">

  266. <dt class="sig sig-object py" id="timeit.default_timer">

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

  268. <dd><p>The default timer, which is always time.perf_counter(), returns float seconds.

  269. An alternative, time.perf_counter_ns, returns integer nanoseconds.</p>

  270. <div class="versionchanged">

  271. <p><span class="versionmodified changed">Changed in version 3.3: </span><a class="reference internal" href="time.html#time.perf_counter" title="time.perf_counter"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.perf_counter()</span></code></a> is now the default timer.</p>

  272. </div>

  273. </dd></dl>

  274. 

  275. <dl class="py class">

  276. <dt class="sig sig-object py" id="timeit.Timer">

  277. <em class="property"><span class="pre">class</span><span class="w"> </span></em><span class="sig-prename descclassname"><span class="pre">timeit.</span></span><span class="sig-name descname"><span class="pre">Timer</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">stmt='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">setup='pass'</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">timer=&lt;timer</span> <span class="pre">function&gt;</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">globals=None</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#timeit.Timer" title="Link to this definition">¶</a></dt>

  278. <dd><p>Class for timing execution speed of small code snippets.</p>

  279. <p>The constructor takes a statement to be timed, an additional statement used

  280. for setup, and a timer function.  Both statements default to <code class="docutils literal notranslate"><span class="pre">'pass'</span></code>;

  281. the timer function is platform-dependent (see the module doc string).

  282. <em>stmt</em> and <em>setup</em> may also contain multiple statements separated by <code class="docutils literal notranslate"><span class="pre">;</span></code>

  283. or newlines, as long as they don’t contain multi-line string literals.  The

  284. statement will by default be executed within timeit’s namespace; this behavior

  285. can be controlled by passing a namespace to <em>globals</em>.</p>

  286. <p>To measure the execution time of the first statement, use the <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a>

  287. method.  The <a class="reference internal" href="#timeit.Timer.repeat" title="timeit.Timer.repeat"><code class="xref py py-meth docutils literal notranslate"><span class="pre">repeat()</span></code></a> and <a class="reference internal" href="#timeit.Timer.autorange" title="timeit.Timer.autorange"><code class="xref py py-meth docutils literal notranslate"><span class="pre">autorange()</span></code></a> methods are convenience

  288. methods to call <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> multiple times.</p>

  289. <p>The execution time of <em>setup</em> is excluded from the overall timed execution run.</p>

  290. <p>The <em>stmt</em> and <em>setup</em> parameters can also take objects that are callable

  291. without arguments.  This will embed calls to them in a timer function that

  292. will then be executed by <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a>.  Note that the timing overhead is a

  293. little larger in this case because of the extra function calls.</p>

  294. <div class="versionchanged">

  295. <p><span class="versionmodified changed">Changed in version 3.5: </span>The optional <em>globals</em> parameter was added.</p>

  296. </div>

  297. <dl class="py method">

  298. <dt class="sig sig-object py" id="timeit.Timer.timeit">

  299. <span class="sig-name descname"><span class="pre">timeit</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">number</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">1000000</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#timeit.Timer.timeit" title="Link to this definition">¶</a></dt>

  300. <dd><p>Time <em>number</em> executions of the main statement.  This executes the setup

  301. statement once, and then returns the time it takes to execute the main

  302. statement a number of times.  The default timer returns seconds as a float.

  303. The argument is the number of times through the loop, defaulting to one

  304. million.  The main statement, the setup statement and the timer function

  305. to be used are passed to the constructor.</p>

  306. <div class="admonition note">

  307. <p class="admonition-title">Note</p>

  308. <p>By default, <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> temporarily turns off <a class="reference internal" href="../glossary.html#term-garbage-collection"><span class="xref std std-term">garbage

  309. collection</span></a> during the timing.  The advantage of this approach is that

  310. it makes independent timings more comparable.  The disadvantage is

  311. that GC may be an important component of the performance of the

  312. function being measured.  If so, GC can be re-enabled as the first

  313. statement in the <em>setup</em> string.  For example:</p>

  314. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">timeit</span><span class="o">.</span><span class="n">Timer</span><span class="p">(</span><span class="s1">&#39;for i in range(10): oct(i)&#39;</span><span class="p">,</span> <span class="s1">&#39;gc.enable()&#39;</span><span class="p">)</span><span class="o">.</span><span class="n">timeit</span><span class="p">()</span>

  315. </pre></div>

  316. </div>

  317. </div>

  318. </dd></dl>

  319. 

  320. <dl class="py method">

  321. <dt class="sig sig-object py" id="timeit.Timer.autorange">

  322. <span class="sig-name descname"><span class="pre">autorange</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">callback</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="#timeit.Timer.autorange" title="Link to this definition">¶</a></dt>

  323. <dd><p>Automatically determine how many times to call <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a>.</p>

  324. <p>This is a convenience function that calls <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> repeatedly

  325. so that the total time &gt;= 0.2 second, returning the eventual

  326. (number of loops, time taken for that number of loops). It calls

  327. <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> with increasing numbers from the sequence 1, 2, 5,

  328. 10, 20, 50, … until the time taken is at least 0.2 seconds.</p>

  329. <p>If <em>callback</em> is given and is not <code class="docutils literal notranslate"><span class="pre">None</span></code>, it will be called after

  330. each trial with two arguments: <code class="docutils literal notranslate"><span class="pre">callback(number,</span> <span class="pre">time_taken)</span></code>.</p>

  331. <div class="versionadded">

  332. <p><span class="versionmodified added">New in version 3.6.</span></p>

  333. </div>

  334. </dd></dl>

  335. 

  336. <dl class="py method">

  337. <dt class="sig sig-object py" id="timeit.Timer.repeat">

  338. <span class="sig-name descname"><span class="pre">repeat</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">repeat</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">5</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">number</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">1000000</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#timeit.Timer.repeat" title="Link to this definition">¶</a></dt>

  339. <dd><p>Call <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> a few times.</p>

  340. <p>This is a convenience function that calls the <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a> repeatedly,

  341. returning a list of results.  The first argument specifies how many times

  342. to call <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a>.  The second argument specifies the <em>number</em>

  343. argument for <a class="reference internal" href="#timeit.Timer.timeit" title="timeit.Timer.timeit"><code class="xref py py-meth docutils literal notranslate"><span class="pre">timeit()</span></code></a>.</p>

  344. <div class="admonition note">

  345. <p class="admonition-title">Note</p>

  346. <p>It’s tempting to calculate mean and standard deviation from the result

  347. vector and report these.  However, this is not very useful.

  348. In a typical case, the lowest value gives a lower bound for how fast

  349. your machine can run the given code snippet; higher values in the

  350. result vector are typically not caused by variability in Python’s

  351. speed, but by other processes interfering with your timing accuracy.

  352. So the <a class="reference internal" href="functions.html#min" title="min"><code class="xref py py-func docutils literal notranslate"><span class="pre">min()</span></code></a> of the result is probably the only number you

  353. should be interested in.  After that, you should look at the entire

  354. vector and apply common sense rather than statistics.</p>

  355. </div>

  356. <div class="versionchanged">

  357. <p><span class="versionmodified changed">Changed in version 3.7: </span>Default value of <em>repeat</em> changed from 3 to 5.</p>

  358. </div>

  359. </dd></dl>

  360. 

  361. <dl class="py method">

  362. <dt class="sig sig-object py" id="timeit.Timer.print_exc">

  363. <span class="sig-name descname"><span class="pre">print_exc</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="#timeit.Timer.print_exc" title="Link to this definition">¶</a></dt>

  364. <dd><p>Helper to print a traceback from the timed code.</p>

  365. <p>Typical use:</p>

  366. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">t</span> <span class="o">=</span> <span class="n">Timer</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>       <span class="c1"># outside the try/except</span>

  367. <span class="k">try</span><span class="p">:</span>

  368.     <span class="n">t</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="o">...</span><span class="p">)</span>    <span class="c1"># or t.repeat(...)</span>

  369. <span class="k">except</span> <span class="ne">Exception</span><span class="p">:</span>

  370.     <span class="n">t</span><span class="o">.</span><span class="n">print_exc</span><span class="p">()</span>

  371. </pre></div>

  372. </div>

  373. <p>The advantage over the standard traceback is that source lines in the

  374. compiled template will be displayed.  The optional <em>file</em> argument directs

  375. where the traceback is sent; it defaults to <a class="reference internal" href="sys.html#sys.stderr" title="sys.stderr"><code class="xref py py-data docutils literal notranslate"><span class="pre">sys.stderr</span></code></a>.</p>

  376. </dd></dl>

  377. 

  378. </dd></dl>

  379. 

  380. </section>

  381. <section id="command-line-interface">

  382. <span id="timeit-command-line-interface"></span><h2>Command-Line Interface<a class="headerlink" href="#command-line-interface" title="Link to this heading">¶</a></h2>

  383. <p>When called as a program from the command line, the following form is used:</p>

  384. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">python</span> <span class="o">-</span><span class="n">m</span> <span class="n">timeit</span> <span class="p">[</span><span class="o">-</span><span class="n">n</span> <span class="n">N</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">r</span> <span class="n">N</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">u</span> <span class="n">U</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">s</span> <span class="n">S</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">p</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">v</span><span class="p">]</span> <span class="p">[</span><span class="o">-</span><span class="n">h</span><span class="p">]</span> <span class="p">[</span><span class="n">statement</span> <span class="o">...</span><span class="p">]</span>

  385. </pre></div>

  386. </div>

  387. <p>Where the following options are understood:</p>

  388. <dl class="std option">

  389. <dt class="sig sig-object std" id="cmdoption-timeit-n">

  390. <span id="cmdoption-timeit-number"></span><span class="sig-name descname"><span class="pre">-n</span></span><span class="sig-prename descclassname"> <span class="pre">N</span></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--number</span></span><span class="sig-prename descclassname"><span class="pre">=N</span></span><a class="headerlink" href="#cmdoption-timeit-n" title="Link to this definition">¶</a></dt>

  391. <dd><p>how many times to execute ‘statement’</p>

  392. </dd></dl>

  393. 

  394. <dl class="std option">

  395. <dt class="sig sig-object std" id="cmdoption-timeit-r">

  396. <span id="cmdoption-timeit-repeat"></span><span class="sig-name descname"><span class="pre">-r</span></span><span class="sig-prename descclassname"> <span class="pre">N</span></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--repeat</span></span><span class="sig-prename descclassname"><span class="pre">=N</span></span><a class="headerlink" href="#cmdoption-timeit-r" title="Link to this definition">¶</a></dt>

  397. <dd><p>how many times to repeat the timer (default 5)</p>

  398. </dd></dl>

  399. 

  400. <dl class="std option">

  401. <dt class="sig sig-object std" id="cmdoption-timeit-s">

  402. <span id="cmdoption-timeit-setup"></span><span class="sig-name descname"><span class="pre">-s</span></span><span class="sig-prename descclassname"> <span class="pre">S</span></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--setup</span></span><span class="sig-prename descclassname"><span class="pre">=S</span></span><a class="headerlink" href="#cmdoption-timeit-s" title="Link to this definition">¶</a></dt>

  403. <dd><p>statement to be executed once initially (default <code class="docutils literal notranslate"><span class="pre">pass</span></code>)</p>

  404. </dd></dl>

  405. 

  406. <dl class="std option">

  407. <dt class="sig sig-object std" id="cmdoption-timeit-p">

  408. <span id="cmdoption-timeit-process"></span><span class="sig-name descname"><span class="pre">-p</span></span><span class="sig-prename descclassname"></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--process</span></span><span class="sig-prename descclassname"></span><a class="headerlink" href="#cmdoption-timeit-p" title="Link to this definition">¶</a></dt>

  409. <dd><p>measure process time, not wallclock time, using <a class="reference internal" href="time.html#time.process_time" title="time.process_time"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.process_time()</span></code></a>

  410. instead of <a class="reference internal" href="time.html#time.perf_counter" title="time.perf_counter"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.perf_counter()</span></code></a>, which is the default</p>

  411. <div class="versionadded">

  412. <p><span class="versionmodified added">New in version 3.3.</span></p>

  413. </div>

  414. </dd></dl>

  415. 

  416. <dl class="std option">

  417. <dt class="sig sig-object std" id="cmdoption-timeit-u">

  418. <span id="cmdoption-timeit-unit"></span><span class="sig-name descname"><span class="pre">-u</span></span><span class="sig-prename descclassname"></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--unit</span></span><span class="sig-prename descclassname"><span class="pre">=U</span></span><a class="headerlink" href="#cmdoption-timeit-u" title="Link to this definition">¶</a></dt>

  419. <dd><p>specify a time unit for timer output; can select <code class="docutils literal notranslate"><span class="pre">nsec</span></code>, <code class="docutils literal notranslate"><span class="pre">usec</span></code>, <code class="docutils literal notranslate"><span class="pre">msec</span></code>, or <code class="docutils literal notranslate"><span class="pre">sec</span></code></p>

  420. <div class="versionadded">

  421. <p><span class="versionmodified added">New in version 3.5.</span></p>

  422. </div>

  423. </dd></dl>

  424. 

  425. <dl class="std option">

  426. <dt class="sig sig-object std" id="cmdoption-timeit-v">

  427. <span id="cmdoption-timeit-verbose"></span><span class="sig-name descname"><span class="pre">-v</span></span><span class="sig-prename descclassname"></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--verbose</span></span><span class="sig-prename descclassname"></span><a class="headerlink" href="#cmdoption-timeit-v" title="Link to this definition">¶</a></dt>

  428. <dd><p>print raw timing results; repeat for more digits precision</p>

  429. </dd></dl>

  430. 

  431. <dl class="std option">

  432. <dt class="sig sig-object std" id="cmdoption-timeit-h">

  433. <span id="cmdoption-timeit-help"></span><span class="sig-name descname"><span class="pre">-h</span></span><span class="sig-prename descclassname"></span><span class="sig-prename descclassname"><span class="pre">,</span> </span><span class="sig-name descname"><span class="pre">--help</span></span><span class="sig-prename descclassname"></span><a class="headerlink" href="#cmdoption-timeit-h" title="Link to this definition">¶</a></dt>

  434. <dd><p>print a short usage message and exit</p>

  435. </dd></dl>

  436. 

  437. <p>A multi-line statement may be given by specifying each line as a separate

  438. statement argument; indented lines are possible by enclosing an argument in

  439. quotes and using leading spaces.  Multiple <a class="reference internal" href="#cmdoption-timeit-s"><code class="xref std std-option docutils literal notranslate"><span class="pre">-s</span></code></a> options are treated

  440. similarly.</p>

  441. <p>If <a class="reference internal" href="#cmdoption-timeit-n"><code class="xref std std-option docutils literal notranslate"><span class="pre">-n</span></code></a> is not given, a suitable number of loops is calculated by trying

  442. increasing numbers from the sequence 1, 2, 5, 10, 20, 50, … until the total

  443. time is at least 0.2 seconds.</p>

  444. <p><a class="reference internal" href="#timeit.default_timer" title="timeit.default_timer"><code class="xref py py-func docutils literal notranslate"><span class="pre">default_timer()</span></code></a> measurements can be affected by other programs running on

  445. the same machine, so the best thing to do when accurate timing is necessary is

  446. to repeat the timing a few times and use the best time.  The <a class="reference internal" href="#cmdoption-timeit-r"><code class="xref std std-option docutils literal notranslate"><span class="pre">-r</span></code></a>

  447. option is good for this; the default of 5 repetitions is probably enough in

  448. most cases.  You can use <a class="reference internal" href="time.html#time.process_time" title="time.process_time"><code class="xref py py-func docutils literal notranslate"><span class="pre">time.process_time()</span></code></a> to measure CPU time.</p>

  449. <div class="admonition note">

  450. <p class="admonition-title">Note</p>

  451. <p>There is a certain baseline overhead associated with executing a pass statement.

  452. The code here doesn’t try to hide it, but you should be aware of it.  The

  453. baseline overhead can be measured by invoking the program without arguments,

  454. and it might differ between Python versions.</p>

  455. </div>

  456. </section>

  457. <section id="examples">

  458. <span id="timeit-examples"></span><h2>Examples<a class="headerlink" href="#examples" title="Link to this heading">¶</a></h2>

  459. <p>It is possible to provide a setup statement that is executed only once at the beginning:</p>

  460. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span>-s<span class="w"> </span><span class="s2">&quot;text = &#39;sample string&#39;; char = &#39;g&#39;&quot;</span><span class="w"> </span><span class="s2">&quot;char in text&quot;</span>

  461. <span class="go">5000000 loops, best of 5: 0.0877 usec per loop</span>

  462. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span>-s<span class="w"> </span><span class="s2">&quot;text = &#39;sample string&#39;; char = &#39;g&#39;&quot;</span><span class="w"> </span><span class="s2">&quot;text.find(char)&quot;</span>

  463. <span class="go">1000000 loops, best of 5: 0.342 usec per loop</span>

  464. </pre></div>

  465. </div>

  466. <p>In the output, there are three fields. The loop count, which tells you how many

  467. times the statement body was run per timing loop repetition. The repetition

  468. count (‘best of 5’) which tells you how many times the timing loop was

  469. repeated, and finally the time the statement body took on average within the

  470. best repetition of the timing loop. That is, the time the fastest repetition

  471. took divided by the loop count.</p>

  472. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">timeit</span>

  473. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;char in text&#39;</span><span class="p">,</span> <span class="n">setup</span><span class="o">=</span><span class="s1">&#39;text = &quot;sample string&quot;; char = &quot;g&quot;&#39;</span><span class="p">)</span>

  474. <span class="go">0.41440500499993504</span>

  475. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;text.find(char)&#39;</span><span class="p">,</span> <span class="n">setup</span><span class="o">=</span><span class="s1">&#39;text = &quot;sample string&quot;; char = &quot;g&quot;&#39;</span><span class="p">)</span>

  476. <span class="go">1.7246671520006203</span>

  477. </pre></div>

  478. </div>

  479. <p>The same can be done using the <a class="reference internal" href="#timeit.Timer" title="timeit.Timer"><code class="xref py py-class docutils literal notranslate"><span class="pre">Timer</span></code></a> class and its methods:</p>

  480. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">timeit</span>

  481. <span class="gp">&gt;&gt;&gt; </span><span class="n">t</span> <span class="o">=</span> <span class="n">timeit</span><span class="o">.</span><span class="n">Timer</span><span class="p">(</span><span class="s1">&#39;char in text&#39;</span><span class="p">,</span> <span class="n">setup</span><span class="o">=</span><span class="s1">&#39;text = &quot;sample string&quot;; char = &quot;g&quot;&#39;</span><span class="p">)</span>

  482. <span class="gp">&gt;&gt;&gt; </span><span class="n">t</span><span class="o">.</span><span class="n">timeit</span><span class="p">()</span>

  483. <span class="go">0.3955516149999312</span>

  484. <span class="gp">&gt;&gt;&gt; </span><span class="n">t</span><span class="o">.</span><span class="n">repeat</span><span class="p">()</span>

  485. <span class="go">[0.40183617287970225, 0.37027556854118704, 0.38344867356679524, 0.3712595970846668, 0.37866875250654886]</span>

  486. </pre></div>

  487. </div>

  488. <p>The following examples show how to time expressions that contain multiple lines.

  489. Here we compare the cost of using <a class="reference internal" href="functions.html#hasattr" title="hasattr"><code class="xref py py-func docutils literal notranslate"><span class="pre">hasattr()</span></code></a> vs. <a class="reference internal" href="../reference/compound_stmts.html#try"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">try</span></code></a>/<a class="reference internal" href="../reference/compound_stmts.html#except"><code class="xref std std-keyword docutils literal notranslate"><span class="pre">except</span></code></a>

  490. to test for missing and present object attributes:</p>

  491. <div class="highlight-shell-session notranslate"><div class="highlight"><pre><span></span><span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;try:&quot;</span><span class="w"> </span><span class="s2">&quot;  str.__bool__&quot;</span><span class="w"> </span><span class="s2">&quot;except AttributeError:&quot;</span><span class="w"> </span><span class="s2">&quot;  pass&quot;</span>

  492. <span class="go">20000 loops, best of 5: 15.7 usec per loop</span>

  493. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;if hasattr(str, &#39;__bool__&#39;): pass&quot;</span>

  494. <span class="go">50000 loops, best of 5: 4.26 usec per loop</span>

  495. 

  496. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;try:&quot;</span><span class="w"> </span><span class="s2">&quot;  int.__bool__&quot;</span><span class="w"> </span><span class="s2">&quot;except AttributeError:&quot;</span><span class="w"> </span><span class="s2">&quot;  pass&quot;</span>

  497. <span class="go">200000 loops, best of 5: 1.43 usec per loop</span>

  498. <span class="gp">$ </span>python<span class="w"> </span>-m<span class="w"> </span>timeit<span class="w"> </span><span class="s2">&quot;if hasattr(int, &#39;__bool__&#39;): pass&quot;</span>

  499. <span class="go">100000 loops, best of 5: 2.23 usec per loop</span>

  500. </pre></div>

  501. </div>

  502. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="gp">&gt;&gt;&gt; </span><span class="kn">import</span> <span class="nn">timeit</span>

  503. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># attribute is missing</span>

  504. <span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;&quot;&quot;</span><span class="se">\</span>

  505. <span class="gp">... </span><span class="s2">try:</span>

  506. <span class="gp">... </span><span class="s2">    str.__bool__</span>

  507. <span class="gp">... </span><span class="s2">except AttributeError:</span>

  508. <span class="gp">... </span><span class="s2">    pass</span>

  509. <span class="gp">... </span><span class="s2">&quot;&quot;&quot;</span>

  510. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="n">stmt</span><span class="o">=</span><span class="n">s</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">100000</span><span class="p">)</span>

  511. <span class="go">0.9138244460009446</span>

  512. <span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;if hasattr(str, &#39;__bool__&#39;): pass&quot;</span>

  513. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="n">stmt</span><span class="o">=</span><span class="n">s</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">100000</span><span class="p">)</span>

  514. <span class="go">0.5829014980008651</span>

  515. <span class="gp">&gt;&gt;&gt;</span>

  516. <span class="gp">&gt;&gt;&gt; </span><span class="c1"># attribute is present</span>

  517. <span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;&quot;&quot;</span><span class="se">\</span>

  518. <span class="gp">... </span><span class="s2">try:</span>

  519. <span class="gp">... </span><span class="s2">    int.__bool__</span>

  520. <span class="gp">... </span><span class="s2">except AttributeError:</span>

  521. <span class="gp">... </span><span class="s2">    pass</span>

  522. <span class="gp">... </span><span class="s2">&quot;&quot;&quot;</span>

  523. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="n">stmt</span><span class="o">=</span><span class="n">s</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">100000</span><span class="p">)</span>

  524. <span class="go">0.04215312199994514</span>

  525. <span class="gp">&gt;&gt;&gt; </span><span class="n">s</span> <span class="o">=</span> <span class="s2">&quot;if hasattr(int, &#39;__bool__&#39;): pass&quot;</span>

  526. <span class="gp">&gt;&gt;&gt; </span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="n">stmt</span><span class="o">=</span><span class="n">s</span><span class="p">,</span> <span class="n">number</span><span class="o">=</span><span class="mi">100000</span><span class="p">)</span>

  527. <span class="go">0.08588060699912603</span>

  528. </pre></div>

  529. </div>

  530. <p>To give the <a class="reference internal" href="#module-timeit" title="timeit: Measure the execution time of small code snippets."><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code></a> module access to functions you define, you can pass a

  531. <em>setup</em> parameter which contains an import statement:</p>

  532. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">test</span><span class="p">():</span>

  533. <span class="w">    </span><span class="sd">&quot;&quot;&quot;Stupid test function&quot;&quot;&quot;</span>

  534.     <span class="n">L</span> <span class="o">=</span> <span class="p">[</span><span class="n">i</span> <span class="k">for</span> <span class="n">i</span> <span class="ow">in</span> <span class="nb">range</span><span class="p">(</span><span class="mi">100</span><span class="p">)]</span>

  535. 

  536. <span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s1">&#39;__main__&#39;</span><span class="p">:</span>

  537.     <span class="kn">import</span> <span class="nn">timeit</span>

  538.     <span class="nb">print</span><span class="p">(</span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s2">&quot;test()&quot;</span><span class="p">,</span> <span class="n">setup</span><span class="o">=</span><span class="s2">&quot;from __main__ import test&quot;</span><span class="p">))</span>

  539. </pre></div>

  540. </div>

  541. <p>Another option is to pass <a class="reference internal" href="functions.html#globals" title="globals"><code class="xref py py-func docutils literal notranslate"><span class="pre">globals()</span></code></a> to the  <em>globals</em> parameter, which will cause the code

  542. to be executed within your current global namespace.  This can be more convenient

  543. than individually specifying imports:</p>

  544. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">f</span><span class="p">(</span><span class="n">x</span><span class="p">):</span>

  545.     <span class="k">return</span> <span class="n">x</span><span class="o">**</span><span class="mi">2</span>

  546. <span class="k">def</span> <span class="nf">g</span><span class="p">(</span><span class="n">x</span><span class="p">):</span>

  547.     <span class="k">return</span> <span class="n">x</span><span class="o">**</span><span class="mi">4</span>

  548. <span class="k">def</span> <span class="nf">h</span><span class="p">(</span><span class="n">x</span><span class="p">):</span>

  549.     <span class="k">return</span> <span class="n">x</span><span class="o">**</span><span class="mi">8</span>

  550. 

  551. <span class="kn">import</span> <span class="nn">timeit</span>

  552. <span class="nb">print</span><span class="p">(</span><span class="n">timeit</span><span class="o">.</span><span class="n">timeit</span><span class="p">(</span><span class="s1">&#39;[func(42) for func in (f,g,h)]&#39;</span><span class="p">,</span> <span class="nb">globals</span><span class="o">=</span><span class="nb">globals</span><span class="p">()))</span>

  553. </pre></div>

  554. </div>

  555. </section>

  556. </section>

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  568. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">timeit</span></code> — Measure execution time of small code snippets</a><ul>

  569. <li><a class="reference internal" href="#basic-examples">Basic Examples</a></li>

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