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  102. <li><a class="reference internal" href="#dictionary-schema-details">Dictionary Schema Details</a></li>

  103. <li><a class="reference internal" href="#incremental-configuration">Incremental Configuration</a></li>

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  206.   <section id="module-logging.config">

  207. <span id="logging-config-logging-configuration"></span><h1><a class="reference internal" href="#module-logging.config" title="logging.config: Configuration of the logging module."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.config</span></code></a> — Logging configuration<a class="headerlink" href="#module-logging.config" title="Link to this heading">¶</a></h1>

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

  209. <aside class="sidebar">

  210. <p class="sidebar-title">Important</p>

  211. <p>This page contains only reference information. For tutorials,

  212. please see</p>

  213. <ul class="simple">

  214. <li><p><a class="reference internal" href="../howto/logging.html#logging-basic-tutorial"><span class="std std-ref">Basic Tutorial</span></a></p></li>

  215. <li><p><a class="reference internal" href="../howto/logging.html#logging-advanced-tutorial"><span class="std std-ref">Advanced Tutorial</span></a></p></li>

  216. <li><p><a class="reference internal" href="../howto/logging-cookbook.html#logging-cookbook"><span class="std std-ref">Logging Cookbook</span></a></p></li>

  217. </ul>

  218. </aside>

  219. <hr class="docutils" />

  220. <p>This section describes the API for configuring the logging module.</p>

  221. <section id="configuration-functions">

  222. <span id="logging-config-api"></span><h2>Configuration functions<a class="headerlink" href="#configuration-functions" title="Link to this heading">¶</a></h2>

  223. <p>The following functions configure the logging module. They are located in the

  224. <a class="reference internal" href="#module-logging.config" title="logging.config: Configuration of the logging module."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.config</span></code></a> module.  Their use is optional — you can configure the

  225. logging module using these functions or by making calls to the main API (defined

  226. in <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> itself) and defining handlers which are declared either in

  227. <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> or <a class="reference internal" href="logging.handlers.html#module-logging.handlers" title="logging.handlers: Handlers for the logging module."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.handlers</span></code></a>.</p>

  228. <dl class="py function">

  229. <dt class="sig sig-object py" id="logging.config.dictConfig">

  230. <span class="sig-prename descclassname"><span class="pre">logging.config.</span></span><span class="sig-name descname"><span class="pre">dictConfig</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">config</span></span></em><span class="sig-paren">)</span><a class="headerlink" href="#logging.config.dictConfig" title="Link to this definition">¶</a></dt>

  231. <dd><p>Takes the logging configuration from a dictionary.  The contents of

  232. this dictionary are described in <a class="reference internal" href="#logging-config-dictschema"><span class="std std-ref">Configuration dictionary schema</span></a>

  233. below.</p>

  234. <p>If an error is encountered during configuration, this function will

  235. raise a <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>, <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>, <a class="reference internal" href="exceptions.html#AttributeError" title="AttributeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">AttributeError</span></code></a>

  236. or <a class="reference internal" href="exceptions.html#ImportError" title="ImportError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">ImportError</span></code></a> with a suitably descriptive message.  The

  237. following is a (possibly incomplete) list of conditions which will

  238. raise an error:</p>

  239. <ul class="simple">

  240. <li><p>A <code class="docutils literal notranslate"><span class="pre">level</span></code> which is not a string or which is a string not

  241. corresponding to an actual logging level.</p></li>

  242. <li><p>A <code class="docutils literal notranslate"><span class="pre">propagate</span></code> value which is not a boolean.</p></li>

  243. <li><p>An id which does not have a corresponding destination.</p></li>

  244. <li><p>A non-existent handler id found during an incremental call.</p></li>

  245. <li><p>An invalid logger name.</p></li>

  246. <li><p>Inability to resolve to an internal or external object.</p></li>

  247. </ul>

  248. <p>Parsing is performed by the <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> class, whose

  249. constructor is passed the dictionary used for configuration, and

  250. has a <code class="xref py py-meth docutils literal notranslate"><span class="pre">configure()</span></code> method.  The <a class="reference internal" href="#module-logging.config" title="logging.config: Configuration of the logging module."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.config</span></code></a> module

  251. has a callable attribute <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code>

  252. which is initially set to <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code>.

  253. You can replace the value of <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code> with a

  254. suitable implementation of your own.</p>

  255. <p><a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> calls <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code> passing

  256. the specified dictionary, and then calls the <code class="xref py py-meth docutils literal notranslate"><span class="pre">configure()</span></code> method on

  257. the returned object to put the configuration into effect:</p>

  258. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span> <span class="nf">dictConfig</span><span class="p">(</span><span class="n">config</span><span class="p">):</span>

  259.     <span class="n">dictConfigClass</span><span class="p">(</span><span class="n">config</span><span class="p">)</span><span class="o">.</span><span class="n">configure</span><span class="p">()</span>

  260. </pre></div>

  261. </div>

  262. <p>For example, a subclass of <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> could call

  263. <code class="docutils literal notranslate"><span class="pre">DictConfigurator.__init__()</span></code> in its own <code class="xref py py-meth docutils literal notranslate"><span class="pre">__init__()</span></code>, then

  264. set up custom prefixes which would be usable in the subsequent

  265. <code class="xref py py-meth docutils literal notranslate"><span class="pre">configure()</span></code> call. <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code> would be bound to

  266. this new subclass, and then <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> could be called exactly as

  267. in the default, uncustomized state.</p>

  268. <div class="versionadded">

  269. <p><span class="versionmodified added">New in version 3.2.</span></p>

  270. </div>

  271. </dd></dl>

  272. 

  273. <dl class="py function">

  274. <dt class="sig sig-object py" id="logging.config.fileConfig">

  275. <span class="sig-prename descclassname"><span class="pre">logging.config.</span></span><span class="sig-name descname"><span class="pre">fileConfig</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">fname</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">defaults</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">disable_existing_loggers</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">True</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">encoding</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="#logging.config.fileConfig" title="Link to this definition">¶</a></dt>

  276. <dd><p>Reads the logging configuration from a <a class="reference internal" href="configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">configparser</span></code></a>-format file. The

  277. format of the file should be as described in

  278. <a class="reference internal" href="#logging-config-fileformat"><span class="std std-ref">Configuration file format</span></a>.

  279. This function can be called several times from an application, allowing an

  280. end user to select from various pre-canned configurations (if the developer

  281. provides a mechanism to present the choices and load the chosen

  282. configuration).</p>

  283. <p>It will raise <a class="reference internal" href="exceptions.html#FileNotFoundError" title="FileNotFoundError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">FileNotFoundError</span></code></a> if the file

  284. doesn’t exist and <a class="reference internal" href="exceptions.html#RuntimeError" title="RuntimeError"><code class="xref py py-exc docutils literal notranslate"><span class="pre">RuntimeError</span></code></a> if the file is invalid or

  285. empty.</p>

  286. <dl class="field-list simple">

  287. <dt class="field-odd">Parameters<span class="colon">:</span></dt>

  288. <dd class="field-odd"><ul class="simple">

  289. <li><p><strong>fname</strong> – A filename, or a file-like object, or an instance derived

  290. from <a class="reference internal" href="configparser.html#configparser.RawConfigParser" title="configparser.RawConfigParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">RawConfigParser</span></code></a>. If a

  291. <code class="xref py py-class docutils literal notranslate"><span class="pre">RawConfigParser</span></code>-derived instance is passed, it is used as

  292. is. Otherwise, a <a class="reference internal" href="configparser.html#configparser.ConfigParser" title="configparser.ConfigParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">ConfigParser</span></code></a> is

  293. instantiated, and the configuration read by it from the

  294. object passed in <code class="docutils literal notranslate"><span class="pre">fname</span></code>. If that has a <a class="reference internal" href="readline.html#module-readline" title="readline: GNU readline support for Python. (Unix)"><code class="xref py py-meth docutils literal notranslate"><span class="pre">readline()</span></code></a>

  295. method, it is assumed to be a file-like object and read using

  296. <a class="reference internal" href="configparser.html#configparser.ConfigParser.read_file" title="configparser.ConfigParser.read_file"><code class="xref py py-meth docutils literal notranslate"><span class="pre">read_file()</span></code></a>; otherwise,

  297. it is assumed to be a filename and passed to

  298. <a class="reference internal" href="configparser.html#configparser.ConfigParser.read" title="configparser.ConfigParser.read"><code class="xref py py-meth docutils literal notranslate"><span class="pre">read()</span></code></a>.</p></li>

  299. <li><p><strong>defaults</strong> – Defaults to be passed to the <code class="xref py py-class docutils literal notranslate"><span class="pre">ConfigParser</span></code> can be specified

  300. in this argument.</p></li>

  301. <li><p><strong>disable_existing_loggers</strong> – If specified as <code class="docutils literal notranslate"><span class="pre">False</span></code>, loggers which

  302. exist when this call is made are left

  303. enabled. The default is <code class="docutils literal notranslate"><span class="pre">True</span></code> because this

  304. enables old behaviour in a

  305. backward-compatible way. This behaviour is to

  306. disable any existing non-root loggers unless

  307. they or their ancestors are explicitly named

  308. in the logging configuration.</p></li>

  309. <li><p><strong>encoding</strong> – The encoding used to open file when <em>fname</em> is filename.</p></li>

  310. </ul>

  311. </dd>

  312. </dl>

  313. <div class="versionchanged">

  314. <p><span class="versionmodified changed">Changed in version 3.4: </span>An instance of a subclass of <a class="reference internal" href="configparser.html#configparser.RawConfigParser" title="configparser.RawConfigParser"><code class="xref py py-class docutils literal notranslate"><span class="pre">RawConfigParser</span></code></a> is

  315.   now accepted as a value for <code class="docutils literal notranslate"><span class="pre">fname</span></code>. This facilitates:</p>

  316. <blockquote>

  317. <div><ul class="simple">

  318. <li><p>Use of a configuration file where logging configuration is just part

  319. of the overall application configuration.</p></li>

  320. <li><p>Use of a configuration read from a file, and then modified by the using

  321. application (e.g. based on command-line parameters or other aspects

  322. of the runtime environment) before being passed to <code class="docutils literal notranslate"><span class="pre">fileConfig</span></code>.</p></li>

  323. </ul>

  324. </div></blockquote>

  325. <div class="versionchanged">

  326. <p><span class="versionmodified changed">Changed in version 3.10: </span>Added the <em>encoding</em> parameter.</p>

  327. </div>

  328. <div class="versionchanged">

  329. <p><span class="versionmodified changed">Changed in version 3.12: </span>An exception will be thrown if the provided file

  330. doesn’t exist or is invalid or empty.</p>

  331. </div>

  332. </div>

  333. </dd></dl>

  334. 

  335. <dl class="py function">

  336. <dt class="sig sig-object py" id="logging.config.listen">

  337. <span class="sig-prename descclassname"><span class="pre">logging.config.</span></span><span class="sig-name descname"><span class="pre">listen</span></span><span class="sig-paren">(</span><em class="sig-param"><span class="n"><span class="pre">port</span></span><span class="o"><span class="pre">=</span></span><span class="default_value"><span class="pre">DEFAULT_LOGGING_CONFIG_PORT</span></span></em>, <em class="sig-param"><span class="n"><span class="pre">verify</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="#logging.config.listen" title="Link to this definition">¶</a></dt>

  338. <dd><p>Starts up a socket server on the specified port, and listens for new

  339. configurations. If no port is specified, the module’s default

  340. <code class="xref py py-const docutils literal notranslate"><span class="pre">DEFAULT_LOGGING_CONFIG_PORT</span></code> is used. Logging configurations will be

  341. sent as a file suitable for processing by <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> or

  342. <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a>. Returns a <a class="reference internal" href="threading.html#threading.Thread" title="threading.Thread"><code class="xref py py-class docutils literal notranslate"><span class="pre">Thread</span></code></a> instance on which

  343. you can call <a class="reference internal" href="threading.html#threading.Thread.start" title="threading.Thread.start"><code class="xref py py-meth docutils literal notranslate"><span class="pre">start()</span></code></a> to start the server, and which

  344. you can <a class="reference internal" href="threading.html#threading.Thread.join" title="threading.Thread.join"><code class="xref py py-meth docutils literal notranslate"><span class="pre">join()</span></code></a> when appropriate. To stop the server,

  345. call <a class="reference internal" href="#logging.config.stopListening" title="logging.config.stopListening"><code class="xref py py-func docutils literal notranslate"><span class="pre">stopListening()</span></code></a>.</p>

  346. <p>The <code class="docutils literal notranslate"><span class="pre">verify</span></code> argument, if specified, should be a callable which should

  347. verify whether bytes received across the socket are valid and should be

  348. processed. This could be done by encrypting and/or signing what is sent

  349. across the socket, such that the <code class="docutils literal notranslate"><span class="pre">verify</span></code> callable can perform

  350. signature verification and/or decryption. The <code class="docutils literal notranslate"><span class="pre">verify</span></code> callable is called

  351. with a single argument - the bytes received across the socket - and should

  352. return the bytes to be processed, or <code class="docutils literal notranslate"><span class="pre">None</span></code> to indicate that the bytes should

  353. be discarded. The returned bytes could be the same as the passed in bytes

  354. (e.g. when only verification is done), or they could be completely different

  355. (perhaps if decryption were performed).</p>

  356. <p>To send a configuration to the socket, read in the configuration file and

  357. send it to the socket as a sequence of bytes preceded by a four-byte length

  358. string packed in binary using <code class="docutils literal notranslate"><span class="pre">struct.pack('&gt;L',</span> <span class="pre">n)</span></code>.</p>

  359. <div class="admonition note" id="logging-eval-security">

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

  361. <p>Because portions of the configuration are passed through

  362. <a class="reference internal" href="functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate"><span class="pre">eval()</span></code></a>, use of this function may open its users to a security risk.

  363. While the function only binds to a socket on <code class="docutils literal notranslate"><span class="pre">localhost</span></code>, and so does

  364. not accept connections from remote machines, there are scenarios where

  365. untrusted code could be run under the account of the process which calls

  366. <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a>. Specifically, if the process calling <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a> runs

  367. on a multi-user machine where users cannot trust each other, then a

  368. malicious user could arrange to run essentially arbitrary code in a

  369. victim user’s process, simply by connecting to the victim’s

  370. <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a> socket and sending a configuration which runs whatever

  371. code the attacker wants to have executed in the victim’s process. This is

  372. especially easy to do if the default port is used, but not hard even if a

  373. different port is used. To avoid the risk of this happening, use the

  374. <code class="docutils literal notranslate"><span class="pre">verify</span></code> argument to <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a> to prevent unrecognised

  375. configurations from being applied.</p>

  376. </div>

  377. <div class="versionchanged">

  378. <p><span class="versionmodified changed">Changed in version 3.4: </span>The <code class="docutils literal notranslate"><span class="pre">verify</span></code> argument was added.</p>

  379. </div>

  380. <div class="admonition note">

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

  382. <p>If you want to send configurations to the listener which don’t

  383. disable existing loggers, you will need to use a JSON format for

  384. the configuration, which will use <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> for configuration.

  385. This method allows you to specify <code class="docutils literal notranslate"><span class="pre">disable_existing_loggers</span></code> as

  386. <code class="docutils literal notranslate"><span class="pre">False</span></code> in the configuration you send.</p>

  387. </div>

  388. </dd></dl>

  389. 

  390. <dl class="py function">

  391. <dt class="sig sig-object py" id="logging.config.stopListening">

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

  393. <dd><p>Stops the listening server which was created with a call to <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a>.

  394. This is typically called before calling <code class="xref py py-meth docutils literal notranslate"><span class="pre">join()</span></code> on the return value from

  395. <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a>.</p>

  396. </dd></dl>

  397. 

  398. </section>

  399. <section id="security-considerations">

  400. <h2>Security considerations<a class="headerlink" href="#security-considerations" title="Link to this heading">¶</a></h2>

  401. <p>The logging configuration functionality tries to offer convenience, and in part this

  402. is done by offering the ability to convert text in configuration files into Python

  403. objects used in logging configuration - for example, as described in

  404. <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>. However, these same mechanisms (importing

  405. callables from user-defined modules and calling them with parameters from the

  406. configuration) could be used to invoke any code you like, and for this reason you

  407. should treat configuration files from untrusted sources with <em>extreme caution</em> and

  408. satisfy yourself that nothing bad can happen if you load them, before actually loading

  409. them.</p>

  410. </section>

  411. <section id="configuration-dictionary-schema">

  412. <span id="logging-config-dictschema"></span><h2>Configuration dictionary schema<a class="headerlink" href="#configuration-dictionary-schema" title="Link to this heading">¶</a></h2>

  413. <p>Describing a logging configuration requires listing the various

  414. objects to create and the connections between them; for example, you

  415. may create a handler named ‘console’ and then say that the logger

  416. named ‘startup’ will send its messages to the ‘console’ handler.

  417. These objects aren’t limited to those provided by the <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a>

  418. module because you might write your own formatter or handler class.

  419. The parameters to these classes may also need to include external

  420. objects such as <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>.  The syntax for describing these

  421. objects and connections is defined in <a class="reference internal" href="#logging-config-dict-connections"><span class="std std-ref">Object connections</span></a>

  422. below.</p>

  423. <section id="dictionary-schema-details">

  424. <h3>Dictionary Schema Details<a class="headerlink" href="#dictionary-schema-details" title="Link to this heading">¶</a></h3>

  425. <p>The dictionary passed to <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> must contain the following

  426. keys:</p>

  427. <ul class="simple">

  428. <li><p><em>version</em> - to be set to an integer value representing the schema

  429. version.  The only valid value at present is 1, but having this key

  430. allows the schema to evolve while still preserving backwards

  431. compatibility.</p></li>

  432. </ul>

  433. <p>All other keys are optional, but if present they will be interpreted

  434. as described below.  In all cases below where a ‘configuring dict’ is

  435. mentioned, it will be checked for the special <code class="docutils literal notranslate"><span class="pre">'()'</span></code> key to see if a

  436. custom instantiation is required.  If so, the mechanism described in

  437. <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a> below is used to create an instance;

  438. otherwise, the context is used to determine what to instantiate.</p>

  439. <ul id="logging-config-dictschema-formatters">

  440. <li><p><em>formatters</em> - the corresponding value will be a dict in which each

  441. key is a formatter id and each value is a dict describing how to

  442. configure the corresponding <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> instance.</p>

  443. <p>The configuring dict is searched for the following optional keys

  444. which correspond to the arguments passed to create a

  445. <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a> object:</p>

  446. <ul class="simple">

  447. <li><p><code class="docutils literal notranslate"><span class="pre">format</span></code></p></li>

  448. <li><p><code class="docutils literal notranslate"><span class="pre">datefmt</span></code></p></li>

  449. <li><p><code class="docutils literal notranslate"><span class="pre">style</span></code></p></li>

  450. <li><p><code class="docutils literal notranslate"><span class="pre">validate</span></code> (since version &gt;=3.8)</p></li>

  451. <li><p><code class="docutils literal notranslate"><span class="pre">defaults</span></code> (since version &gt;=3.12)</p></li>

  452. </ul>

  453. <p>An optional <code class="docutils literal notranslate"><span class="pre">class</span></code> key indicates the name of the formatter’s

  454. class (as a dotted module and class name).  The instantiation

  455. arguments are as for <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a>, thus this key is

  456. most useful for instantiating a customised subclass of

  457. <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Formatter</span></code></a>.  For example, the alternative class

  458. might present exception tracebacks in an expanded or condensed

  459. format.  If your formatter requires different or extra configuration

  460. keys, you should use <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>.</p>

  461. </li>

  462. <li><p><em>filters</em> - the corresponding value will be a dict in which each key

  463. is a filter id and each value is a dict describing how to configure

  464. the corresponding Filter instance.</p>

  465. <p>The configuring dict is searched for the key <code class="docutils literal notranslate"><span class="pre">name</span></code> (defaulting to the

  466. empty string) and this is used to construct a <a class="reference internal" href="logging.html#logging.Filter" title="logging.Filter"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.Filter</span></code></a>

  467. instance.</p>

  468. </li>

  469. <li><p><em>handlers</em> - the corresponding value will be a dict in which each

  470. key is a handler id and each value is a dict describing how to

  471. configure the corresponding Handler instance.</p>

  472. <p>The configuring dict is searched for the following keys:</p>

  473. <ul>

  474. <li><p><code class="docutils literal notranslate"><span class="pre">class</span></code> (mandatory).  This is the fully qualified name of the

  475. handler class.</p></li>

  476. <li><p><code class="docutils literal notranslate"><span class="pre">level</span></code> (optional).  The level of the handler.</p></li>

  477. <li><p><code class="docutils literal notranslate"><span class="pre">formatter</span></code> (optional).  The id of the formatter for this

  478. handler.</p></li>

  479. <li><p><code class="docutils literal notranslate"><span class="pre">filters</span></code> (optional).  A list of ids of the filters for this

  480. handler.</p>

  481. <div class="versionchanged">

  482. <p><span class="versionmodified changed">Changed in version 3.11: </span><code class="docutils literal notranslate"><span class="pre">filters</span></code> can take filter instances in addition to ids.</p>

  483. </div>

  484. </li>

  485. </ul>

  486. <p>All <em>other</em> keys are passed through as keyword arguments to the

  487. handler’s constructor.  For example, given the snippet:</p>

  488. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>

  489. <span class="w">  </span><span class="nt">console</span><span class="p">:</span>

  490. <span class="w">    </span><span class="nt">class </span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">logging.StreamHandler</span>

  491. <span class="w">    </span><span class="nt">formatter</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">brief</span>

  492. <span class="w">    </span><span class="nt">level   </span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">INFO</span>

  493. <span class="w">    </span><span class="nt">filters</span><span class="p">:</span><span class="w"> </span><span class="p p-Indicator">[</span><span class="nv">allow_foo</span><span class="p p-Indicator">]</span>

  494. <span class="w">    </span><span class="nt">stream  </span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">ext://sys.stdout</span>

  495. <span class="w">  </span><span class="nt">file</span><span class="p">:</span>

  496. <span class="w">    </span><span class="nt">class </span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">logging.handlers.RotatingFileHandler</span>

  497. <span class="w">    </span><span class="nt">formatter</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">precise</span>

  498. <span class="w">    </span><span class="nt">filename</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">logconfig.log</span>

  499. <span class="w">    </span><span class="nt">maxBytes</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">1024</span>

  500. <span class="w">    </span><span class="nt">backupCount</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">3</span>

  501. </pre></div>

  502. </div>

  503. <p>the handler with id <code class="docutils literal notranslate"><span class="pre">console</span></code> is instantiated as a

  504. <a class="reference internal" href="logging.handlers.html#logging.StreamHandler" title="logging.StreamHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.StreamHandler</span></code></a>, using <code class="docutils literal notranslate"><span class="pre">sys.stdout</span></code> as the underlying

  505. stream.  The handler with id <code class="docutils literal notranslate"><span class="pre">file</span></code> is instantiated as a

  506. <a class="reference internal" href="logging.handlers.html#logging.handlers.RotatingFileHandler" title="logging.handlers.RotatingFileHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.handlers.RotatingFileHandler</span></code></a> with the keyword arguments

  507. <code class="docutils literal notranslate"><span class="pre">filename='logconfig.log',</span> <span class="pre">maxBytes=1024,</span> <span class="pre">backupCount=3</span></code>.</p>

  508. </li>

  509. <li><p><em>loggers</em> - the corresponding value will be a dict in which each key

  510. is a logger name and each value is a dict describing how to

  511. configure the corresponding Logger instance.</p>

  512. <p>The configuring dict is searched for the following keys:</p>

  513. <ul>

  514. <li><p><code class="docutils literal notranslate"><span class="pre">level</span></code> (optional).  The level of the logger.</p></li>

  515. <li><p><code class="docutils literal notranslate"><span class="pre">propagate</span></code> (optional).  The propagation setting of the logger.</p></li>

  516. <li><p><code class="docutils literal notranslate"><span class="pre">filters</span></code> (optional).  A list of ids of the filters for this

  517. logger.</p>

  518. <div class="versionchanged">

  519. <p><span class="versionmodified changed">Changed in version 3.11: </span><code class="docutils literal notranslate"><span class="pre">filters</span></code> can take filter instances in addition to ids.</p>

  520. </div>

  521. </li>

  522. <li><p><code class="docutils literal notranslate"><span class="pre">handlers</span></code> (optional).  A list of ids of the handlers for this

  523. logger.</p></li>

  524. </ul>

  525. <p>The specified loggers will be configured according to the level,

  526. propagation, filters and handlers specified.</p>

  527. </li>

  528. <li><p><em>root</em> - this will be the configuration for the root logger.

  529. Processing of the configuration will be as for any logger, except

  530. that the <code class="docutils literal notranslate"><span class="pre">propagate</span></code> setting will not be applicable.</p></li>

  531. <li><p><em>incremental</em> - whether the configuration is to be interpreted as

  532. incremental to the existing configuration.  This value defaults to

  533. <code class="docutils literal notranslate"><span class="pre">False</span></code>, which means that the specified configuration replaces the

  534. existing configuration with the same semantics as used by the

  535. existing <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a> API.</p>

  536. <p>If the specified value is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the configuration is processed

  537. as described in the section on <a class="reference internal" href="#logging-config-dict-incremental"><span class="std std-ref">Incremental Configuration</span></a>.</p>

  538. </li>

  539. <li><p><em>disable_existing_loggers</em> - whether any existing non-root loggers are

  540. to be disabled. This setting mirrors the parameter of the same name in

  541. <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a>. If absent, this parameter defaults to <code class="docutils literal notranslate"><span class="pre">True</span></code>.

  542. This value is ignored if <em>incremental</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p></li>

  543. </ul>

  544. </section>

  545. <section id="incremental-configuration">

  546. <span id="logging-config-dict-incremental"></span><h3>Incremental Configuration<a class="headerlink" href="#incremental-configuration" title="Link to this heading">¶</a></h3>

  547. <p>It is difficult to provide complete flexibility for incremental

  548. configuration.  For example, because objects such as filters

  549. and formatters are anonymous, once a configuration is set up, it is

  550. not possible to refer to such anonymous objects when augmenting a

  551. configuration.</p>

  552. <p>Furthermore, there is not a compelling case for arbitrarily altering

  553. the object graph of loggers, handlers, filters, formatters at

  554. run-time, once a configuration is set up; the verbosity of loggers and

  555. handlers can be controlled just by setting levels (and, in the case of

  556. loggers, propagation flags).  Changing the object graph arbitrarily in

  557. a safe way is problematic in a multi-threaded environment; while not

  558. impossible, the benefits are not worth the complexity it adds to the

  559. implementation.</p>

  560. <p>Thus, when the <code class="docutils literal notranslate"><span class="pre">incremental</span></code> key of a configuration dict is present

  561. and is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the system will completely ignore any <code class="docutils literal notranslate"><span class="pre">formatters</span></code> and

  562. <code class="docutils literal notranslate"><span class="pre">filters</span></code> entries, and process only the <code class="docutils literal notranslate"><span class="pre">level</span></code>

  563. settings in the <code class="docutils literal notranslate"><span class="pre">handlers</span></code> entries, and the <code class="docutils literal notranslate"><span class="pre">level</span></code> and

  564. <code class="docutils literal notranslate"><span class="pre">propagate</span></code> settings in the <code class="docutils literal notranslate"><span class="pre">loggers</span></code> and <code class="docutils literal notranslate"><span class="pre">root</span></code> entries.</p>

  565. <p>Using a value in the configuration dict lets configurations to be sent

  566. over the wire as pickled dicts to a socket listener. Thus, the logging

  567. verbosity of a long-running application can be altered over time with

  568. no need to stop and restart the application.</p>

  569. </section>

  570. <section id="object-connections">

  571. <span id="logging-config-dict-connections"></span><h3>Object connections<a class="headerlink" href="#object-connections" title="Link to this heading">¶</a></h3>

  572. <p>The schema describes a set of logging objects - loggers,

  573. handlers, formatters, filters - which are connected to each other in

  574. an object graph.  Thus, the schema needs to represent connections

  575. between the objects.  For example, say that, once configured, a

  576. particular logger has attached to it a particular handler.  For the

  577. purposes of this discussion, we can say that the logger represents the

  578. source, and the handler the destination, of a connection between the

  579. two.  Of course in the configured objects this is represented by the

  580. logger holding a reference to the handler.  In the configuration dict,

  581. this is done by giving each destination object an id which identifies

  582. it unambiguously, and then using the id in the source object’s

  583. configuration to indicate that a connection exists between the source

  584. and the destination object with that id.</p>

  585. <p>So, for example, consider the following YAML snippet:</p>

  586. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">formatters</span><span class="p">:</span>

  587. <span class="w">  </span><span class="nt">brief</span><span class="p">:</span>

  588. <span class="w">    </span><span class="c1"># configuration for formatter with id &#39;brief&#39; goes here</span>

  589. <span class="w">  </span><span class="nt">precise</span><span class="p">:</span>

  590. <span class="w">    </span><span class="c1"># configuration for formatter with id &#39;precise&#39; goes here</span>

  591. <span class="nt">handlers</span><span class="p">:</span>

  592. <span class="w">  </span><span class="nt">h1</span><span class="p">:</span><span class="w"> </span><span class="c1">#This is an id</span>

  593. <span class="w">   </span><span class="c1"># configuration of handler with id &#39;h1&#39; goes here</span>

  594. <span class="w">   </span><span class="nt">formatter</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">brief</span>

  595. <span class="w">  </span><span class="nt">h2</span><span class="p">:</span><span class="w"> </span><span class="c1">#This is another id</span>

  596. <span class="w">   </span><span class="c1"># configuration of handler with id &#39;h2&#39; goes here</span>

  597. <span class="w">   </span><span class="nt">formatter</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">precise</span>

  598. <span class="nt">loggers</span><span class="p">:</span>

  599. <span class="w">  </span><span class="nt">foo.bar.baz</span><span class="p">:</span>

  600. <span class="w">    </span><span class="c1"># other configuration for logger &#39;foo.bar.baz&#39;</span>

  601. <span class="w">    </span><span class="nt">handlers</span><span class="p">:</span><span class="w"> </span><span class="p p-Indicator">[</span><span class="nv">h1</span><span class="p p-Indicator">,</span><span class="w"> </span><span class="nv">h2</span><span class="p p-Indicator">]</span>

  602. </pre></div>

  603. </div>

  604. <p>(Note: YAML used here because it’s a little more readable than the

  605. equivalent Python source form for the dictionary.)</p>

  606. <p>The ids for loggers are the logger names which would be used

  607. programmatically to obtain a reference to those loggers, e.g.

  608. <code class="docutils literal notranslate"><span class="pre">foo.bar.baz</span></code>.  The ids for Formatters and Filters can be any string

  609. value (such as <code class="docutils literal notranslate"><span class="pre">brief</span></code>, <code class="docutils literal notranslate"><span class="pre">precise</span></code> above) and they are transient,

  610. in that they are only meaningful for processing the configuration

  611. dictionary and used to determine connections between objects, and are

  612. not persisted anywhere when the configuration call is complete.</p>

  613. <p>The above snippet indicates that logger named <code class="docutils literal notranslate"><span class="pre">foo.bar.baz</span></code> should

  614. have two handlers attached to it, which are described by the handler

  615. ids <code class="docutils literal notranslate"><span class="pre">h1</span></code> and <code class="docutils literal notranslate"><span class="pre">h2</span></code>. The formatter for <code class="docutils literal notranslate"><span class="pre">h1</span></code> is that described by id

  616. <code class="docutils literal notranslate"><span class="pre">brief</span></code>, and the formatter for <code class="docutils literal notranslate"><span class="pre">h2</span></code> is that described by id

  617. <code class="docutils literal notranslate"><span class="pre">precise</span></code>.</p>

  618. </section>

  619. <section id="user-defined-objects">

  620. <span id="logging-config-dict-userdef"></span><h3>User-defined objects<a class="headerlink" href="#user-defined-objects" title="Link to this heading">¶</a></h3>

  621. <p>The schema supports user-defined objects for handlers, filters and

  622. formatters.  (Loggers do not need to have different types for

  623. different instances, so there is no support in this configuration

  624. schema for user-defined logger classes.)</p>

  625. <p>Objects to be configured are described by dictionaries

  626. which detail their configuration.  In some places, the logging system

  627. will be able to infer from the context how an object is to be

  628. instantiated, but when a user-defined object is to be instantiated,

  629. the system will not know how to do this.  In order to provide complete

  630. flexibility for user-defined object instantiation, the user needs

  631. to provide a ‘factory’ - a callable which is called with a

  632. configuration dictionary and which returns the instantiated object.

  633. This is signalled by an absolute import path to the factory being

  634. made available under the special key <code class="docutils literal notranslate"><span class="pre">'()'</span></code>.  Here’s a concrete

  635. example:</p>

  636. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">formatters</span><span class="p">:</span>

  637. <span class="w">  </span><span class="nt">brief</span><span class="p">:</span>

  638. <span class="w">    </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s">&#39;%(message)s&#39;</span>

  639. <span class="w">  </span><span class="nt">default</span><span class="p">:</span>

  640. <span class="w">    </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s">&#39;%(asctime)s</span><span class="nv"> </span><span class="s">%(levelname)-8s</span><span class="nv"> </span><span class="s">%(name)-15s</span><span class="nv"> </span><span class="s">%(message)s&#39;</span>

  641. <span class="w">    </span><span class="nt">datefmt</span><span class="p">:</span><span class="w"> </span><span class="s">&#39;%Y-%m-%d</span><span class="nv"> </span><span class="s">%H:%M:%S&#39;</span>

  642. <span class="w">  </span><span class="nt">custom</span><span class="p">:</span>

  643. <span class="w">      </span><span class="nt">()</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">my.package.customFormatterFactory</span>

  644. <span class="w">      </span><span class="nt">bar</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">baz</span>

  645. <span class="w">      </span><span class="nt">spam</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">99.9</span>

  646. <span class="w">      </span><span class="nt">answer</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">42</span>

  647. </pre></div>

  648. </div>

  649. <p>The above YAML snippet defines three formatters.  The first, with id

  650. <code class="docutils literal notranslate"><span class="pre">brief</span></code>, is a standard <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.Formatter</span></code></a> instance with the

  651. specified format string.  The second, with id <code class="docutils literal notranslate"><span class="pre">default</span></code>, has a

  652. longer format and also defines the time format explicitly, and will

  653. result in a <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.Formatter</span></code></a> initialized with those two format

  654. strings.  Shown in Python source form, the <code class="docutils literal notranslate"><span class="pre">brief</span></code> and <code class="docutils literal notranslate"><span class="pre">default</span></code>

  655. formatters have configuration sub-dictionaries:</p>

  656. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>

  657.   <span class="s1">&#39;format&#39;</span> <span class="p">:</span> <span class="s1">&#39;</span><span class="si">%(message)s</span><span class="s1">&#39;</span>

  658. <span class="p">}</span>

  659. </pre></div>

  660. </div>

  661. <p>and:</p>

  662. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>

  663.   <span class="s1">&#39;format&#39;</span> <span class="p">:</span> <span class="s1">&#39;</span><span class="si">%(asctime)s</span><span class="s1"> </span><span class="si">%(levelname)-8s</span><span class="s1"> </span><span class="si">%(name)-15s</span><span class="s1"> </span><span class="si">%(message)s</span><span class="s1">&#39;</span><span class="p">,</span>

  664.   <span class="s1">&#39;datefmt&#39;</span> <span class="p">:</span> <span class="s1">&#39;%Y-%m-</span><span class="si">%d</span><span class="s1"> %H:%M:%S&#39;</span>

  665. <span class="p">}</span>

  666. </pre></div>

  667. </div>

  668. <p>respectively, and as these dictionaries do not contain the special key

  669. <code class="docutils literal notranslate"><span class="pre">'()'</span></code>, the instantiation is inferred from the context: as a result,

  670. standard <a class="reference internal" href="logging.html#logging.Formatter" title="logging.Formatter"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.Formatter</span></code></a> instances are created.  The

  671. configuration sub-dictionary for the third formatter, with id

  672. <code class="docutils literal notranslate"><span class="pre">custom</span></code>, is:</p>

  673. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>

  674.   <span class="s1">&#39;()&#39;</span> <span class="p">:</span> <span class="s1">&#39;my.package.customFormatterFactory&#39;</span><span class="p">,</span>

  675.   <span class="s1">&#39;bar&#39;</span> <span class="p">:</span> <span class="s1">&#39;baz&#39;</span><span class="p">,</span>

  676.   <span class="s1">&#39;spam&#39;</span> <span class="p">:</span> <span class="mf">99.9</span><span class="p">,</span>

  677.   <span class="s1">&#39;answer&#39;</span> <span class="p">:</span> <span class="mi">42</span>

  678. <span class="p">}</span>

  679. </pre></div>

  680. </div>

  681. <p>and this contains the special key <code class="docutils literal notranslate"><span class="pre">'()'</span></code>, which means that

  682. user-defined instantiation is wanted.  In this case, the specified

  683. factory callable will be used. If it is an actual callable it will be

  684. used directly - otherwise, if you specify a string (as in the example)

  685. the actual callable will be located using normal import mechanisms.

  686. The callable will be called with the <strong>remaining</strong> items in the

  687. configuration sub-dictionary as keyword arguments.  In the above

  688. example, the formatter with id <code class="docutils literal notranslate"><span class="pre">custom</span></code> will be assumed to be

  689. returned by the call:</p>

  690. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="n">my</span><span class="o">.</span><span class="n">package</span><span class="o">.</span><span class="n">customFormatterFactory</span><span class="p">(</span><span class="n">bar</span><span class="o">=</span><span class="s1">&#39;baz&#39;</span><span class="p">,</span> <span class="n">spam</span><span class="o">=</span><span class="mf">99.9</span><span class="p">,</span> <span class="n">answer</span><span class="o">=</span><span class="mi">42</span><span class="p">)</span>

  691. </pre></div>

  692. </div>

  693. <div class="admonition warning">

  694. <p class="admonition-title">Warning</p>

  695. <p>The values for keys such as <code class="docutils literal notranslate"><span class="pre">bar</span></code>, <code class="docutils literal notranslate"><span class="pre">spam</span></code> and <code class="docutils literal notranslate"><span class="pre">answer</span></code> in

  696. the above example should not be configuration dictionaries or references such

  697. as <code class="docutils literal notranslate"><span class="pre">cfg://foo</span></code> or <code class="docutils literal notranslate"><span class="pre">ext://bar</span></code>, because they will not be processed by the

  698. configuration machinery, but passed to the callable as-is.</p>

  699. </div>

  700. <p>The key <code class="docutils literal notranslate"><span class="pre">'()'</span></code> has been used as the special key because it is not a

  701. valid keyword parameter name, and so will not clash with the names of

  702. the keyword arguments used in the call.  The <code class="docutils literal notranslate"><span class="pre">'()'</span></code> also serves as a

  703. mnemonic that the corresponding value is a callable.</p>

  704. <div class="versionchanged">

  705. <p><span class="versionmodified changed">Changed in version 3.11: </span>The <code class="docutils literal notranslate"><span class="pre">filters</span></code> member of <code class="docutils literal notranslate"><span class="pre">handlers</span></code> and <code class="docutils literal notranslate"><span class="pre">loggers</span></code> can take

  706. filter instances in addition to ids.</p>

  707. </div>

  708. <p>You can also specify a special key <code class="docutils literal notranslate"><span class="pre">'.'</span></code> whose value is a dictionary is a

  709. mapping of attribute names to values. If found, the specified attributes will

  710. be set on the user-defined object before it is returned. Thus, with the

  711. following configuration:</p>

  712. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>

  713.   <span class="s1">&#39;()&#39;</span> <span class="p">:</span> <span class="s1">&#39;my.package.customFormatterFactory&#39;</span><span class="p">,</span>

  714.   <span class="s1">&#39;bar&#39;</span> <span class="p">:</span> <span class="s1">&#39;baz&#39;</span><span class="p">,</span>

  715.   <span class="s1">&#39;spam&#39;</span> <span class="p">:</span> <span class="mf">99.9</span><span class="p">,</span>

  716.   <span class="s1">&#39;answer&#39;</span> <span class="p">:</span> <span class="mi">42</span><span class="p">,</span>

  717.   <span class="s1">&#39;.&#39;</span> <span class="p">{</span>

  718.     <span class="s1">&#39;foo&#39;</span><span class="p">:</span> <span class="s1">&#39;bar&#39;</span><span class="p">,</span>

  719.     <span class="s1">&#39;baz&#39;</span><span class="p">:</span> <span class="s1">&#39;bozz&#39;</span>

  720.   <span class="p">}</span>

  721. <span class="p">}</span>

  722. </pre></div>

  723. </div>

  724. <p>the returned formatter will have attribute <code class="docutils literal notranslate"><span class="pre">foo</span></code> set to <code class="docutils literal notranslate"><span class="pre">'bar'</span></code> and

  725. attribute <code class="docutils literal notranslate"><span class="pre">baz</span></code> set to <code class="docutils literal notranslate"><span class="pre">'bozz'</span></code>.</p>

  726. <div class="admonition warning">

  727. <p class="admonition-title">Warning</p>

  728. <p>The values for attributes such as <code class="docutils literal notranslate"><span class="pre">foo</span></code> and <code class="docutils literal notranslate"><span class="pre">baz</span></code> in

  729. the above example should not be configuration dictionaries or references such

  730. as <code class="docutils literal notranslate"><span class="pre">cfg://foo</span></code> or <code class="docutils literal notranslate"><span class="pre">ext://bar</span></code>, because they will not be processed by the

  731. configuration machinery, but set as attribute values as-is.</p>

  732. </div>

  733. </section>

  734. <section id="handler-configuration-order">

  735. <span id="handler-config-dict-order"></span><h3>Handler configuration order<a class="headerlink" href="#handler-configuration-order" title="Link to this heading">¶</a></h3>

  736. <p>Handlers are configured in alphabetical order of their keys, and a configured

  737. handler replaces the configuration dictionary in (a working copy of) the

  738. <code class="docutils literal notranslate"><span class="pre">handlers</span></code> dictionary in the schema. If you use a construct such as

  739. <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code>, then initially <code class="docutils literal notranslate"><span class="pre">handlers['foo']</span></code> points to the

  740. configuration dictionary for the handler named <code class="docutils literal notranslate"><span class="pre">foo</span></code>, and later (once that

  741. handler has been configured) it points to the configured handler instance.

  742. Thus, <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code> could resolve to either a dictionary or a handler

  743. instance. In general, it is wise to name handlers in a way such that dependent

  744. handlers are configured _after_ any handlers they depend on; that allows

  745. something like <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code> to be used in configuring a handler that

  746. depends on handler <code class="docutils literal notranslate"><span class="pre">foo</span></code>. If that dependent handler were named <code class="docutils literal notranslate"><span class="pre">bar</span></code>,

  747. problems would result, because the configuration of <code class="docutils literal notranslate"><span class="pre">bar</span></code> would be attempted

  748. before that of <code class="docutils literal notranslate"><span class="pre">foo</span></code>, and <code class="docutils literal notranslate"><span class="pre">foo</span></code> would not yet have been configured.

  749. However, if the dependent handler were named <code class="docutils literal notranslate"><span class="pre">foobar</span></code>, it would be configured

  750. after <code class="docutils literal notranslate"><span class="pre">foo</span></code>, with the result that <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code> would resolve to

  751. configured handler <code class="docutils literal notranslate"><span class="pre">foo</span></code>, and not its configuration dictionary.</p>

  752. </section>

  753. <section id="access-to-external-objects">

  754. <span id="logging-config-dict-externalobj"></span><h3>Access to external objects<a class="headerlink" href="#access-to-external-objects" title="Link to this heading">¶</a></h3>

  755. <p>There are times where a configuration needs to refer to objects

  756. external to the configuration, for example <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>.  If the

  757. configuration dict is constructed using Python code, this is

  758. straightforward, but a problem arises when the configuration is

  759. provided via a text file (e.g. JSON, YAML).  In a text file, there is

  760. no standard way to distinguish <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code> from the literal string

  761. <code class="docutils literal notranslate"><span class="pre">'sys.stderr'</span></code>.  To facilitate this distinction, the configuration

  762. system looks for certain special prefixes in string values and

  763. treat them specially.  For example, if the literal string

  764. <code class="docutils literal notranslate"><span class="pre">'ext://sys.stderr'</span></code> is provided as a value in the configuration,

  765. then the <code class="docutils literal notranslate"><span class="pre">ext://</span></code> will be stripped off and the remainder of the

  766. value processed using normal import mechanisms.</p>

  767. <p>The handling of such prefixes is done in a way analogous to protocol

  768. handling: there is a generic mechanism to look for prefixes which

  769. match the regular expression <code class="docutils literal notranslate"><span class="pre">^(?P&lt;prefix&gt;[a-z]+)://(?P&lt;suffix&gt;.*)$</span></code>

  770. whereby, if the <code class="docutils literal notranslate"><span class="pre">prefix</span></code> is recognised, the <code class="docutils literal notranslate"><span class="pre">suffix</span></code> is processed

  771. in a prefix-dependent manner and the result of the processing replaces

  772. the string value.  If the prefix is not recognised, then the string

  773. value will be left as-is.</p>

  774. </section>

  775. <section id="access-to-internal-objects">

  776. <span id="logging-config-dict-internalobj"></span><h3>Access to internal objects<a class="headerlink" href="#access-to-internal-objects" title="Link to this heading">¶</a></h3>

  777. <p>As well as external objects, there is sometimes also a need to refer

  778. to objects in the configuration.  This will be done implicitly by the

  779. configuration system for things that it knows about.  For example, the

  780. string value <code class="docutils literal notranslate"><span class="pre">'DEBUG'</span></code> for a <code class="docutils literal notranslate"><span class="pre">level</span></code> in a logger or handler will

  781. automatically be converted to the value <code class="docutils literal notranslate"><span class="pre">logging.DEBUG</span></code>, and the

  782. <code class="docutils literal notranslate"><span class="pre">handlers</span></code>, <code class="docutils literal notranslate"><span class="pre">filters</span></code> and <code class="docutils literal notranslate"><span class="pre">formatter</span></code> entries will take an

  783. object id and resolve to the appropriate destination object.</p>

  784. <p>However, a more generic mechanism is needed for user-defined

  785. objects which are not known to the <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a> module.  For

  786. example, consider <a class="reference internal" href="logging.handlers.html#logging.handlers.MemoryHandler" title="logging.handlers.MemoryHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.handlers.MemoryHandler</span></code></a>, which takes

  787. a <code class="docutils literal notranslate"><span class="pre">target</span></code> argument which is another handler to delegate to. Since

  788. the system already knows about this class, then in the configuration,

  789. the given <code class="docutils literal notranslate"><span class="pre">target</span></code> just needs to be the object id of the relevant

  790. target handler, and the system will resolve to the handler from the

  791. id.  If, however, a user defines a <code class="docutils literal notranslate"><span class="pre">my.package.MyHandler</span></code> which has

  792. an <code class="docutils literal notranslate"><span class="pre">alternate</span></code> handler, the configuration system would not know that

  793. the <code class="docutils literal notranslate"><span class="pre">alternate</span></code> referred to a handler.  To cater for this, a generic

  794. resolution system allows the user to specify:</p>

  795. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>

  796. <span class="w">  </span><span class="nt">file</span><span class="p">:</span>

  797. <span class="w">    </span><span class="c1"># configuration of file handler goes here</span>

  798. 

  799. <span class="w">  </span><span class="nt">custom</span><span class="p">:</span>

  800. <span class="w">    </span><span class="nt">()</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">my.package.MyHandler</span>

  801. <span class="w">    </span><span class="nt">alternate</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">cfg://handlers.file</span>

  802. </pre></div>

  803. </div>

  804. <p>The literal string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.file'</span></code> will be resolved in an

  805. analogous way to strings with the <code class="docutils literal notranslate"><span class="pre">ext://</span></code> prefix, but looking

  806. in the configuration itself rather than the import namespace.  The

  807. mechanism allows access by dot or by index, in a similar way to

  808. that provided by <code class="docutils literal notranslate"><span class="pre">str.format</span></code>.  Thus, given the following snippet:</p>

  809. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>

  810. <span class="w">  </span><span class="nt">email</span><span class="p">:</span>

  811. <span class="w">    </span><span class="nt">class</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">logging.handlers.SMTPHandler</span>

  812. <span class="w">    </span><span class="nt">mailhost</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">localhost</span>

  813. <span class="w">    </span><span class="nt">fromaddr</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">my_app@domain.tld</span>

  814. <span class="w">    </span><span class="nt">toaddrs</span><span class="p">:</span>

  815. <span class="w">      </span><span class="p p-Indicator">-</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">support_team@domain.tld</span>

  816. <span class="w">      </span><span class="p p-Indicator">-</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">dev_team@domain.tld</span>

  817. <span class="w">    </span><span class="nt">subject</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">Houston, we have a problem.</span>

  818. </pre></div>

  819. </div>

  820. <p>in the configuration, the string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers'</span></code> would resolve to

  821. the dict with key <code class="docutils literal notranslate"><span class="pre">handlers</span></code>, the string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email</span></code>

  822. would resolve to the dict with key <code class="docutils literal notranslate"><span class="pre">email</span></code> in the <code class="docutils literal notranslate"><span class="pre">handlers</span></code> dict,

  823. and so on.  The string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.toaddrs[1]</span></code> would

  824. resolve to <code class="docutils literal notranslate"><span class="pre">'dev_team&#64;domain.tld'</span></code> and the string

  825. <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.toaddrs[0]'</span></code> would resolve to the value

  826. <code class="docutils literal notranslate"><span class="pre">'support_team&#64;domain.tld'</span></code>. The <code class="docutils literal notranslate"><span class="pre">subject</span></code> value could be accessed

  827. using either <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.subject'</span></code> or, equivalently,

  828. <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email[subject]'</span></code>.  The latter form only needs to be

  829. used if the key contains spaces or non-alphanumeric characters.  If an

  830. index value consists only of decimal digits, access will be attempted

  831. using the corresponding integer value, falling back to the string

  832. value if needed.</p>

  833. <p>Given a string <code class="docutils literal notranslate"><span class="pre">cfg://handlers.myhandler.mykey.123</span></code>, this will

  834. resolve to <code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey']['123']</span></code>.

  835. If the string is specified as <code class="docutils literal notranslate"><span class="pre">cfg://handlers.myhandler.mykey[123]</span></code>,

  836. the system will attempt to retrieve the value from

  837. <code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey'][123]</span></code>, and fall back

  838. to <code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey']['123']</span></code> if that

  839. fails.</p>

  840. </section>

  841. <section id="import-resolution-and-custom-importers">

  842. <span id="logging-import-resolution"></span><h3>Import resolution and custom importers<a class="headerlink" href="#import-resolution-and-custom-importers" title="Link to this heading">¶</a></h3>

  843. <p>Import resolution, by default, uses the builtin <a class="reference internal" href="functions.html#import__" title="__import__"><code class="xref py py-func docutils literal notranslate"><span class="pre">__import__()</span></code></a> function

  844. to do its importing. You may want to replace this with your own importing

  845. mechanism: if so, you can replace the <code class="xref py py-attr docutils literal notranslate"><span class="pre">importer</span></code> attribute of the

  846. <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> or its superclass, the

  847. <code class="xref py py-class docutils literal notranslate"><span class="pre">BaseConfigurator</span></code> class. However, you need to be

  848. careful because of the way functions are accessed from classes via

  849. descriptors. If you are using a Python callable to do your imports, and you

  850. want to define it at class level rather than instance level, you need to wrap

  851. it with <a class="reference internal" href="functions.html#staticmethod" title="staticmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">staticmethod()</span></code></a>. For example:</p>

  852. <div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">importlib</span> <span class="kn">import</span> <span class="n">import_module</span>

  853. <span class="kn">from</span> <span class="nn">logging.config</span> <span class="kn">import</span> <span class="n">BaseConfigurator</span>

  854. 

  855. <span class="n">BaseConfigurator</span><span class="o">.</span><span class="n">importer</span> <span class="o">=</span> <span class="nb">staticmethod</span><span class="p">(</span><span class="n">import_module</span><span class="p">)</span>

  856. </pre></div>

  857. </div>

  858. <p>You don’t need to wrap with <a class="reference internal" href="functions.html#staticmethod" title="staticmethod"><code class="xref py py-func docutils literal notranslate"><span class="pre">staticmethod()</span></code></a> if you’re setting the import

  859. callable on a configurator <em>instance</em>.</p>

  860. </section>

  861. <section id="configuring-queuehandler-and-queuelistener">

  862. <span id="configure-queue"></span><h3>Configuring QueueHandler and QueueListener<a class="headerlink" href="#configuring-queuehandler-and-queuelistener" title="Link to this heading">¶</a></h3>

  863. <p>If you want to configure a <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueHandler" title="logging.handlers.QueueHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">QueueHandler</span></code></a>, noting that this

  864. is normally used in conjunction with a <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueListener" title="logging.handlers.QueueListener"><code class="xref py py-class docutils literal notranslate"><span class="pre">QueueListener</span></code></a>, you

  865. can configure both together. After the configuration, the <code class="docutils literal notranslate"><span class="pre">QueueListener</span></code> instance

  866. will be available as the <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueHandler.listener" title="logging.handlers.QueueHandler.listener"><code class="xref py py-attr docutils literal notranslate"><span class="pre">listener</span></code></a> attribute of

  867. the created handler, and that in turn will be available to you using

  868. <a class="reference internal" href="logging.html#logging.getHandlerByName" title="logging.getHandlerByName"><code class="xref py py-func docutils literal notranslate"><span class="pre">getHandlerByName()</span></code></a> and passing the name you have used for the

  869. <code class="docutils literal notranslate"><span class="pre">QueueHandler</span></code> in your configuration. The dictionary schema for configuring the pair

  870. is shown in the example YAML snippet below.</p>

  871. <div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>

  872. <span class="w">  </span><span class="nt">qhand</span><span class="p">:</span>

  873. <span class="w">    </span><span class="nt">class</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">logging.handlers.QueueHandler</span>

  874. <span class="w">    </span><span class="nt">queue</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">my.module.queue_factory</span>

  875. <span class="w">    </span><span class="nt">listener</span><span class="p">:</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">my.package.CustomListener</span>

  876. <span class="w">    </span><span class="nt">handlers</span><span class="p">:</span>

  877. <span class="w">      </span><span class="p p-Indicator">-</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">hand_name_1</span>

  878. <span class="w">      </span><span class="p p-Indicator">-</span><span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">hand_name_2</span>

  879. <span class="w">      </span><span class="l l-Scalar l-Scalar-Plain">...</span>

  880. </pre></div>

  881. </div>

  882. <p>The <code class="docutils literal notranslate"><span class="pre">queue</span></code> and <code class="docutils literal notranslate"><span class="pre">listener</span></code> keys are optional.</p>

  883. <p>If the <code class="docutils literal notranslate"><span class="pre">queue</span></code> key is present, the corresponding value can be one of the following:</p>

  884. <ul class="simple">

  885. <li><p>An actual instance of <a class="reference internal" href="queue.html#queue.Queue" title="queue.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">queue.Queue</span></code></a> or a subclass thereof. This is of course

  886. only possible if you are constructing or modifying the configuration dictionary in

  887. code.</p></li>

  888. <li><p>A string that resolves to a callable which, when called with no arguments, returns

  889. the <a class="reference internal" href="queue.html#queue.Queue" title="queue.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">queue.Queue</span></code></a> instance to use. That callable could be a

  890. <a class="reference internal" href="queue.html#queue.Queue" title="queue.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">queue.Queue</span></code></a> subclass or a function which returns a suitable queue instance,

  891. such as <code class="docutils literal notranslate"><span class="pre">my.module.queue_factory()</span></code>.</p></li>

  892. <li><p>A dict with a <code class="docutils literal notranslate"><span class="pre">'()'</span></code> key which is constructed in the usual way as discussed in

  893. <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>. The result of this construction should be a

  894. <a class="reference internal" href="queue.html#queue.Queue" title="queue.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">queue.Queue</span></code></a> instance.</p></li>

  895. </ul>

  896. <p>If the  <code class="docutils literal notranslate"><span class="pre">queue</span></code> key is absent, a standard unbounded <a class="reference internal" href="queue.html#queue.Queue" title="queue.Queue"><code class="xref py py-class docutils literal notranslate"><span class="pre">queue.Queue</span></code></a> instance is

  897. created and used.</p>

  898. <p>If the <code class="docutils literal notranslate"><span class="pre">listener</span></code> key is present, the corresponding value can be one of the following:</p>

  899. <ul class="simple">

  900. <li><p>A subclass of <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueListener" title="logging.handlers.QueueListener"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.handlers.QueueListener</span></code></a>. This is of course only

  901. possible if you are constructing or modifying the configuration dictionary in

  902. code.</p></li>

  903. <li><p>A string which resolves to a class which is a subclass of <code class="docutils literal notranslate"><span class="pre">QueueListener</span></code>, such as

  904. <code class="docutils literal notranslate"><span class="pre">'my.package.CustomListener'</span></code>.</p></li>

  905. <li><p>A dict with a <code class="docutils literal notranslate"><span class="pre">'()'</span></code> key which is constructed in the usual way as discussed in

  906. <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>. The result of this construction should be a

  907. callable with the same signature as the <code class="docutils literal notranslate"><span class="pre">QueueListener</span></code> initializer.</p></li>

  908. </ul>

  909. <p>If the <code class="docutils literal notranslate"><span class="pre">listener</span></code> key is absent, <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueListener" title="logging.handlers.QueueListener"><code class="xref py py-class docutils literal notranslate"><span class="pre">logging.handlers.QueueListener</span></code></a> is used.</p>

  910. <p>The values under the <code class="docutils literal notranslate"><span class="pre">handlers</span></code> key are the names of other handlers in the

  911. configuration (not shown in the above snippet) which will be passed to the queue

  912. listener.</p>

  913. <p>Any custom queue handler and listener classes will need to be defined with the same

  914. initialization signatures as <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueHandler" title="logging.handlers.QueueHandler"><code class="xref py py-class docutils literal notranslate"><span class="pre">QueueHandler</span></code></a> and

  915. <a class="reference internal" href="logging.handlers.html#logging.handlers.QueueListener" title="logging.handlers.QueueListener"><code class="xref py py-class docutils literal notranslate"><span class="pre">QueueListener</span></code></a>.</p>

  916. <div class="versionadded">

  917. <p><span class="versionmodified added">New in version 3.12.</span></p>

  918. </div>

  919. </section>

  920. </section>

  921. <section id="configuration-file-format">

  922. <span id="logging-config-fileformat"></span><h2>Configuration file format<a class="headerlink" href="#configuration-file-format" title="Link to this heading">¶</a></h2>

  923. <p>The configuration file format understood by <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a> is based on

  924. <a class="reference internal" href="configparser.html#module-configparser" title="configparser: Configuration file parser."><code class="xref py py-mod docutils literal notranslate"><span class="pre">configparser</span></code></a> functionality. The file must contain sections called

  925. <code class="docutils literal notranslate"><span class="pre">[loggers]</span></code>, <code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> and <code class="docutils literal notranslate"><span class="pre">[formatters]</span></code> which identify by name the

  926. entities of each type which are defined in the file. For each such entity, there

  927. is a separate section which identifies how that entity is configured.  Thus, for

  928. a logger named <code class="docutils literal notranslate"><span class="pre">log01</span></code> in the <code class="docutils literal notranslate"><span class="pre">[loggers]</span></code> section, the relevant

  929. configuration details are held in a section <code class="docutils literal notranslate"><span class="pre">[logger_log01]</span></code>. Similarly, a

  930. handler called <code class="docutils literal notranslate"><span class="pre">hand01</span></code> in the <code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> section will have its

  931. configuration held in a section called <code class="docutils literal notranslate"><span class="pre">[handler_hand01]</span></code>, while a formatter

  932. called <code class="docutils literal notranslate"><span class="pre">form01</span></code> in the <code class="docutils literal notranslate"><span class="pre">[formatters]</span></code> section will have its configuration

  933. specified in a section called <code class="docutils literal notranslate"><span class="pre">[formatter_form01]</span></code>. The root logger

  934. configuration must be specified in a section called <code class="docutils literal notranslate"><span class="pre">[logger_root]</span></code>.</p>

  935. <div class="admonition note">

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

  937. <p>The <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a> API is older than the <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a> API and does

  938. not provide functionality to cover certain aspects of logging. For example,

  939. you cannot configure <a class="reference internal" href="logging.html#logging.Filter" title="logging.Filter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Filter</span></code></a> objects, which provide for

  940. filtering of messages beyond simple integer levels, using <a class="reference internal" href="#logging.config.fileConfig" title="logging.config.fileConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">fileConfig()</span></code></a>.

  941. If you need to have instances of <a class="reference internal" href="logging.html#logging.Filter" title="logging.Filter"><code class="xref py py-class docutils literal notranslate"><span class="pre">Filter</span></code></a> in your logging

  942. configuration, you will need to use <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a>. Note that future

  943. enhancements to configuration functionality will be added to

  944. <a class="reference internal" href="#logging.config.dictConfig" title="logging.config.dictConfig"><code class="xref py py-func docutils literal notranslate"><span class="pre">dictConfig()</span></code></a>, so it’s worth considering transitioning to this newer

  945. API when it’s convenient to do so.</p>

  946. </div>

  947. <p>Examples of these sections in the file are given below.</p>

  948. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[loggers]</span>

  949. <span class="na">keys</span><span class="o">=</span><span class="s">root,log02,log03,log04,log05,log06,log07</span>

  950. 

  951. <span class="k">[handlers]</span>

  952. <span class="na">keys</span><span class="o">=</span><span class="s">hand01,hand02,hand03,hand04,hand05,hand06,hand07,hand08,hand09</span>

  953. 

  954. <span class="k">[formatters]</span>

  955. <span class="na">keys</span><span class="o">=</span><span class="s">form01,form02,form03,form04,form05,form06,form07,form08,form09</span>

  956. </pre></div>

  957. </div>

  958. <p>The root logger must specify a level and a list of handlers. An example of a

  959. root logger section is given below.</p>

  960. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[logger_root]</span>

  961. <span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>

  962. <span class="na">handlers</span><span class="o">=</span><span class="s">hand01</span>

  963. </pre></div>

  964. </div>

  965. <p>The <code class="docutils literal notranslate"><span class="pre">level</span></code> entry can be one of <code class="docutils literal notranslate"><span class="pre">DEBUG,</span> <span class="pre">INFO,</span> <span class="pre">WARNING,</span> <span class="pre">ERROR,</span> <span class="pre">CRITICAL</span></code> or

  966. <code class="docutils literal notranslate"><span class="pre">NOTSET</span></code>. For the root logger only, <code class="docutils literal notranslate"><span class="pre">NOTSET</span></code> means that all messages will be

  967. logged. Level values are <a class="reference internal" href="functions.html#func-eval"><span class="std std-ref">evaluated</span></a> in the context of the <code class="docutils literal notranslate"><span class="pre">logging</span></code>

  968. package’s namespace.</p>

  969. <p>The <code class="docutils literal notranslate"><span class="pre">handlers</span></code> entry is a comma-separated list of handler names, which must

  970. appear in the <code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> section. These names must appear in the

  971. <code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> section and have corresponding sections in the configuration

  972. file.</p>

  973. <p>For loggers other than the root logger, some additional information is required.

  974. This is illustrated by the following example.</p>

  975. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[logger_parser]</span>

  976. <span class="na">level</span><span class="o">=</span><span class="s">DEBUG</span>

  977. <span class="na">handlers</span><span class="o">=</span><span class="s">hand01</span>

  978. <span class="na">propagate</span><span class="o">=</span><span class="s">1</span>

  979. <span class="na">qualname</span><span class="o">=</span><span class="s">compiler.parser</span>

  980. </pre></div>

  981. </div>

  982. <p>The <code class="docutils literal notranslate"><span class="pre">level</span></code> and <code class="docutils literal notranslate"><span class="pre">handlers</span></code> entries are interpreted as for the root logger,

  983. except that if a non-root logger’s level is specified as <code class="docutils literal notranslate"><span class="pre">NOTSET</span></code>, the system

  984. consults loggers higher up the hierarchy to determine the effective level of the

  985. logger. The <code class="docutils literal notranslate"><span class="pre">propagate</span></code> entry is set to 1 to indicate that messages must

  986. propagate to handlers higher up the logger hierarchy from this logger, or 0 to

  987. indicate that messages are <strong>not</strong> propagated to handlers up the hierarchy. The

  988. <code class="docutils literal notranslate"><span class="pre">qualname</span></code> entry is the hierarchical channel name of the logger, that is to

  989. say the name used by the application to get the logger.</p>

  990. <p>Sections which specify handler configuration are exemplified by the following.</p>

  991. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[handler_hand01]</span>

  992. <span class="na">class</span><span class="o">=</span><span class="s">StreamHandler</span>

  993. <span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>

  994. <span class="na">formatter</span><span class="o">=</span><span class="s">form01</span>

  995. <span class="na">args</span><span class="o">=</span><span class="s">(sys.stdout,)</span>

  996. </pre></div>

  997. </div>

  998. <p>The <code class="docutils literal notranslate"><span class="pre">class</span></code> entry indicates the handler’s class (as determined by <a class="reference internal" href="functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate"><span class="pre">eval()</span></code></a>

  999. in the <code class="docutils literal notranslate"><span class="pre">logging</span></code> package’s namespace). The <code class="docutils literal notranslate"><span class="pre">level</span></code> is interpreted as for

  1000. loggers, and <code class="docutils literal notranslate"><span class="pre">NOTSET</span></code> is taken to mean ‘log everything’.</p>

  1001. <p>The <code class="docutils literal notranslate"><span class="pre">formatter</span></code> entry indicates the key name of the formatter for this

  1002. handler. If blank, a default formatter (<code class="docutils literal notranslate"><span class="pre">logging._defaultFormatter</span></code>) is used.

  1003. If a name is specified, it must appear in the <code class="docutils literal notranslate"><span class="pre">[formatters]</span></code> section and have

  1004. a corresponding section in the configuration file.</p>

  1005. <p>The <code class="docutils literal notranslate"><span class="pre">args</span></code> entry, when <a class="reference internal" href="functions.html#func-eval"><span class="std std-ref">evaluated</span></a> in the context of the <code class="docutils literal notranslate"><span class="pre">logging</span></code>

  1006. package’s namespace, is the list of arguments to the constructor for the handler

  1007. class. Refer to the constructors for the relevant handlers, or to the examples

  1008. below, to see how typical entries are constructed. If not provided, it defaults

  1009. to <code class="docutils literal notranslate"><span class="pre">()</span></code>.</p>

  1010. <p>The optional <code class="docutils literal notranslate"><span class="pre">kwargs</span></code> entry, when <a class="reference internal" href="functions.html#func-eval"><span class="std std-ref">evaluated</span></a> in the context of the

  1011. <code class="docutils literal notranslate"><span class="pre">logging</span></code> package’s namespace, is the keyword argument dict to the constructor

  1012. for the handler class. If not provided, it defaults to <code class="docutils literal notranslate"><span class="pre">{}</span></code>.</p>

  1013. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[handler_hand02]</span>

  1014. <span class="na">class</span><span class="o">=</span><span class="s">FileHandler</span>

  1015. <span class="na">level</span><span class="o">=</span><span class="s">DEBUG</span>

  1016. <span class="na">formatter</span><span class="o">=</span><span class="s">form02</span>

  1017. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;python.log&#39;, &#39;w&#39;)</span>

  1018. 

  1019. <span class="k">[handler_hand03]</span>

  1020. <span class="na">class</span><span class="o">=</span><span class="s">handlers.SocketHandler</span>

  1021. <span class="na">level</span><span class="o">=</span><span class="s">INFO</span>

  1022. <span class="na">formatter</span><span class="o">=</span><span class="s">form03</span>

  1023. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;localhost&#39;, handlers.DEFAULT_TCP_LOGGING_PORT)</span>

  1024. 

  1025. <span class="k">[handler_hand04]</span>

  1026. <span class="na">class</span><span class="o">=</span><span class="s">handlers.DatagramHandler</span>

  1027. <span class="na">level</span><span class="o">=</span><span class="s">WARN</span>

  1028. <span class="na">formatter</span><span class="o">=</span><span class="s">form04</span>

  1029. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;localhost&#39;, handlers.DEFAULT_UDP_LOGGING_PORT)</span>

  1030. 

  1031. <span class="k">[handler_hand05]</span>

  1032. <span class="na">class</span><span class="o">=</span><span class="s">handlers.SysLogHandler</span>

  1033. <span class="na">level</span><span class="o">=</span><span class="s">ERROR</span>

  1034. <span class="na">formatter</span><span class="o">=</span><span class="s">form05</span>

  1035. <span class="na">args</span><span class="o">=</span><span class="s">((&#39;localhost&#39;, handlers.SYSLOG_UDP_PORT), handlers.SysLogHandler.LOG_USER)</span>

  1036. 

  1037. <span class="k">[handler_hand06]</span>

  1038. <span class="na">class</span><span class="o">=</span><span class="s">handlers.NTEventLogHandler</span>

  1039. <span class="na">level</span><span class="o">=</span><span class="s">CRITICAL</span>

  1040. <span class="na">formatter</span><span class="o">=</span><span class="s">form06</span>

  1041. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;Python Application&#39;, &#39;&#39;, &#39;Application&#39;)</span>

  1042. 

  1043. <span class="k">[handler_hand07]</span>

  1044. <span class="na">class</span><span class="o">=</span><span class="s">handlers.SMTPHandler</span>

  1045. <span class="na">level</span><span class="o">=</span><span class="s">WARN</span>

  1046. <span class="na">formatter</span><span class="o">=</span><span class="s">form07</span>

  1047. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;localhost&#39;, &#39;from@abc&#39;, [&#39;user1@abc&#39;, &#39;user2@xyz&#39;], &#39;Logger Subject&#39;)</span>

  1048. <span class="na">kwargs</span><span class="o">=</span><span class="s">{&#39;timeout&#39;: 10.0}</span>

  1049. 

  1050. <span class="k">[handler_hand08]</span>

  1051. <span class="na">class</span><span class="o">=</span><span class="s">handlers.MemoryHandler</span>

  1052. <span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>

  1053. <span class="na">formatter</span><span class="o">=</span><span class="s">form08</span>

  1054. <span class="na">target</span><span class="o">=</span>

  1055. <span class="na">args</span><span class="o">=</span><span class="s">(10, ERROR)</span>

  1056. 

  1057. <span class="k">[handler_hand09]</span>

  1058. <span class="na">class</span><span class="o">=</span><span class="s">handlers.HTTPHandler</span>

  1059. <span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>

  1060. <span class="na">formatter</span><span class="o">=</span><span class="s">form09</span>

  1061. <span class="na">args</span><span class="o">=</span><span class="s">(&#39;localhost:9022&#39;, &#39;/log&#39;, &#39;GET&#39;)</span>

  1062. <span class="na">kwargs</span><span class="o">=</span><span class="s">{&#39;secure&#39;: True}</span>

  1063. </pre></div>

  1064. </div>

  1065. <p>Sections which specify formatter configuration are typified by the following.</p>

  1066. <div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[formatter_form01]</span>

  1067. <span class="na">format</span><span class="o">=</span><span class="s">F1 %(asctime)s %(levelname)s %(message)s %(customfield)s</span>

  1068. <span class="na">datefmt</span><span class="o">=</span>

  1069. <span class="na">style</span><span class="o">=</span><span class="s">%</span>

  1070. <span class="na">validate</span><span class="o">=</span><span class="s">True</span>

  1071. <span class="na">defaults</span><span class="o">=</span><span class="s">{&#39;customfield&#39;: &#39;defaultvalue&#39;}</span>

  1072. <span class="na">class</span><span class="o">=</span><span class="s">logging.Formatter</span>

  1073. </pre></div>

  1074. </div>

  1075. <p>The arguments for the formatter configuration are the same as the keys

  1076. in the dictionary schema <a class="reference internal" href="#logging-config-dictschema-formatters"><span class="std std-ref">formatters section</span></a>.</p>

  1077. <p>The <code class="docutils literal notranslate"><span class="pre">defaults</span></code> entry, when <a class="reference internal" href="functions.html#func-eval"><span class="std std-ref">evaluated</span></a> in the context of

  1078. the <code class="docutils literal notranslate"><span class="pre">logging</span></code> package’s namespace, is a dictionary of default values for

  1079. custom formatting fields. If not provided, it defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>

  1080. <div class="admonition note">

  1081. <p class="admonition-title">Note</p>

  1082. <p>Due to the use of <a class="reference internal" href="functions.html#eval" title="eval"><code class="xref py py-func docutils literal notranslate"><span class="pre">eval()</span></code></a> as described above, there are

  1083. potential security risks which result from using the <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a> to send

  1084. and receive configurations via sockets. The risks are limited to where

  1085. multiple users with no mutual trust run code on the same machine; see the

  1086. <a class="reference internal" href="#logging.config.listen" title="logging.config.listen"><code class="xref py py-func docutils literal notranslate"><span class="pre">listen()</span></code></a> documentation for more information.</p>

  1087. </div>

  1088. <div class="admonition seealso">

  1089. <p class="admonition-title">See also</p>

  1090. <dl class="simple">

  1091. <dt>Module <a class="reference internal" href="logging.html#module-logging" title="logging: Flexible event logging system for applications."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code></a></dt><dd><p>API reference for the logging module.</p>

  1092. </dd>

  1093. <dt>Module <a class="reference internal" href="logging.handlers.html#module-logging.handlers" title="logging.handlers: Handlers for the logging module."><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.handlers</span></code></a></dt><dd><p>Useful handlers included with the logging module.</p>

  1094. </dd>

  1095. </dl>

  1096. </div>

  1097. </section>

  1098. </section>

  1099. 

  1100. 

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  1106.         <div class="sphinxsidebarwrapper">

  1107.   <div>

  1108.     <h3><a href="../contents.html">Table of Contents</a></h3>

  1109.     <ul>

  1110. <li><a class="reference internal" href="#"><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.config</span></code> — Logging configuration</a><ul>

  1111. <li><a class="reference internal" href="#configuration-functions">Configuration functions</a></li>

  1112. <li><a class="reference internal" href="#security-considerations">Security considerations</a></li>

  1113. <li><a class="reference internal" href="#configuration-dictionary-schema">Configuration dictionary schema</a><ul>

  1114. <li><a class="reference internal" href="#dictionary-schema-details">Dictionary Schema Details</a></li>

  1115. <li><a class="reference internal" href="#incremental-configuration">Incremental Configuration</a></li>

  1116. <li><a class="reference internal" href="#object-connections">Object connections</a></li>

  1117. <li><a class="reference internal" href="#user-defined-objects">User-defined objects</a></li>

  1118. <li><a class="reference internal" href="#handler-configuration-order">Handler configuration order</a></li>

  1119. <li><a class="reference internal" href="#access-to-external-objects">Access to external objects</a></li>

  1120. <li><a class="reference internal" href="#access-to-internal-objects">Access to internal objects</a></li>

  1121. <li><a class="reference internal" href="#import-resolution-and-custom-importers">Import resolution and custom importers</a></li>

  1122. <li><a class="reference internal" href="#configuring-queuehandler-and-queuelistener">Configuring QueueHandler and QueueListener</a></li>

  1123. </ul>

  1124. </li>

  1125. <li><a class="reference internal" href="#configuration-file-format">Configuration file format</a></li>

  1126. </ul>

  1127. </li>

  1128. </ul>

  1129. 

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  1133.     <p class="topless"><a href="logging.html"

  1134.                           title="previous chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging</span></code> — Logging facility for Python</a></p>

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  1137.     <h4>Next topic</h4>

  1138.     <p class="topless"><a href="logging.handlers.html"

  1139.                           title="next chapter"><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.handlers</span></code> — Logging handlers</a></p>

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