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<ul>
<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>
<li><a class="reference internal" href="#configuration-functions">Configuration functions</a></li>
<li><a class="reference internal" href="#security-considerations">Security considerations</a></li>
<li><a class="reference internal" href="#configuration-dictionary-schema">Configuration dictionary schema</a><ul>
<li><a class="reference internal" href="#dictionary-schema-details">Dictionary Schema Details</a></li>
<li><a class="reference internal" href="#incremental-configuration">Incremental Configuration</a></li>
<li><a class="reference internal" href="#object-connections">Object connections</a></li>
<li><a class="reference internal" href="#user-defined-objects">User-defined objects</a></li>
<li><a class="reference internal" href="#handler-configuration-order">Handler configuration order</a></li>
<li><a class="reference internal" href="#access-to-external-objects">Access to external objects</a></li>
<li><a class="reference internal" href="#access-to-internal-objects">Access to internal objects</a></li>
<li><a class="reference internal" href="#import-resolution-and-custom-importers">Import resolution and custom importers</a></li>
<li><a class="reference internal" href="#configuring-queuehandler-and-queuelistener">Configuring QueueHandler and QueueListener</a></li>
</ul>
</li>
<li><a class="reference internal" href="#configuration-file-format">Configuration file format</a></li>
</ul>
</li>
</ul>
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<section id="module-logging.config">
<span id="logging-config-logging-configuration"></span><h1><code class="xref py py-mod docutils literal notranslate"><span class="pre">logging.config</span></code> — Logging configuration<a class="headerlink" href="#module-logging.config" title="Link to this heading">¶</a></h1>
<p><strong>Source code:</strong> <a class="extlink-source reference external" href="https://github.com/python/cpython/tree/3.13/Lib/logging/config.py">Lib/logging/config.py</a></p>
<aside class="sidebar">
<p class="sidebar-title">Important</p>
<p>This page contains only reference information. For tutorials,
please see</p>
<ul class="simple">
<li><p><a class="reference internal" href="../howto/logging.html#logging-basic-tutorial"><span class="std std-ref">Basic Tutorial</span></a></p></li>
<li><p><a class="reference internal" href="../howto/logging.html#logging-advanced-tutorial"><span class="std std-ref">Advanced Tutorial</span></a></p></li>
<li><p><a class="reference internal" href="../howto/logging-cookbook.html#logging-cookbook"><span class="std std-ref">Logging Cookbook</span></a></p></li>
</ul>
</aside>
<hr class="docutils" />
<p>This section describes the API for configuring the logging module.</p>
<section id="configuration-functions">
<span id="logging-config-api"></span><h2>Configuration functions<a class="headerlink" href="#configuration-functions" title="Link to this heading">¶</a></h2>
<p>The following functions configure the logging module. They are located in 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. Their use is optional — you can configure the
logging module using these functions or by making calls to the main API (defined
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
<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>
<dl class="py function">
<dt class="sig sig-object py" id="logging.config.dictConfig">
<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>
<dd><p>Takes the logging configuration from a dictionary. The contents of
this dictionary are described in <a class="reference internal" href="#logging-config-dictschema"><span class="std std-ref">Configuration dictionary schema</span></a>
below.</p>
<p>If an error is encountered during configuration, this function will
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>
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
following is a (possibly incomplete) list of conditions which will
raise an error:</p>
<ul class="simple">
<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
corresponding to an actual logging level.</p></li>
<li><p>A <code class="docutils literal notranslate"><span class="pre">propagate</span></code> value which is not a boolean.</p></li>
<li><p>An id which does not have a corresponding destination.</p></li>
<li><p>A non-existent handler id found during an incremental call.</p></li>
<li><p>An invalid logger name.</p></li>
<li><p>Inability to resolve to an internal or external object.</p></li>
</ul>
<p>Parsing is performed by the <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> class, whose
constructor is passed the dictionary used for configuration, and
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
has a callable attribute <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code>
which is initially set to <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code>.
You can replace the value of <code class="xref py py-attr docutils literal notranslate"><span class="pre">dictConfigClass</span></code> with a
suitable implementation of your own.</p>
<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
the specified dictionary, and then calls the <code class="xref py py-meth docutils literal notranslate"><span class="pre">configure()</span></code> method on
the returned object to put the configuration into effect:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="k">def</span><span class="w"> </span><span class="nf">dictConfig</span><span class="p">(</span><span class="n">config</span><span class="p">):</span>
<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>
</pre></div>
</div>
<p>For example, a subclass of <code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> could call
<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
set up custom prefixes which would be usable in the subsequent
<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
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
in the default, uncustomized state.</p>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.2.</span></p>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="logging.config.fileConfig">
<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>
<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
format of the file should be as described in
<a class="reference internal" href="#logging-config-fileformat"><span class="std std-ref">Configuration file format</span></a>.
This function can be called several times from an application, allowing an
end user to select from various pre-canned configurations (if the developer
provides a mechanism to present the choices and load the chosen
configuration).</p>
<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
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
empty.</p>
<dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>fname</strong> – A filename, or a file-like object, or an instance derived
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
<code class="xref py py-class docutils literal notranslate"><span class="pre">RawConfigParser</span></code>-derived instance is passed, it is used as
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
instantiated, and the configuration read by it from the
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>
method, it is assumed to be a file-like object and read using
<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,
it is assumed to be a filename and passed to
<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>
<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
in this argument.</p></li>
<li><p><strong>disable_existing_loggers</strong> – If specified as <code class="docutils literal notranslate"><span class="pre">False</span></code>, loggers which
exist when this call is made are left
enabled. The default is <code class="docutils literal notranslate"><span class="pre">True</span></code> because this
enables old behaviour in a
backward-compatible way. This behaviour is to
disable any existing non-root loggers unless
they or their ancestors are explicitly named
in the logging configuration.</p></li>
<li><p><strong>encoding</strong> – The encoding used to open file when <em>fname</em> is filename.</p></li>
</ul>
</dd>
</dl>
<div class="versionchanged">
<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
now accepted as a value for <code class="docutils literal notranslate"><span class="pre">fname</span></code>. This facilitates:</p>
<blockquote>
<div><ul class="simple">
<li><p>Use of a configuration file where logging configuration is just part
of the overall application configuration.</p></li>
<li><p>Use of a configuration read from a file, and then modified by the using
application (e.g. based on command-line parameters or other aspects
of the runtime environment) before being passed to <code class="docutils literal notranslate"><span class="pre">fileConfig</span></code>.</p></li>
</ul>
</div></blockquote>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.10: </span>Added the <em>encoding</em> parameter.</p>
</div>
<div class="versionchanged">
<p><span class="versionmodified changed">Changed in version 3.12: </span>An exception will be thrown if the provided file
doesn’t exist or is invalid or empty.</p>
</div>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="logging.config.listen">
<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>
<dd><p>Starts up a socket server on the specified port, and listens for new
configurations. If no port is specified, the module’s default
<code class="xref py py-const docutils literal notranslate"><span class="pre">DEFAULT_LOGGING_CONFIG_PORT</span></code> is used. Logging configurations will be
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
<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
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
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,
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>
<p>The <code class="docutils literal notranslate"><span class="pre">verify</span></code> argument, if specified, should be a callable which should
verify whether bytes received across the socket are valid and should be
processed. This could be done by encrypting and/or signing what is sent
across the socket, such that the <code class="docutils literal notranslate"><span class="pre">verify</span></code> callable can perform
signature verification and/or decryption. The <code class="docutils literal notranslate"><span class="pre">verify</span></code> callable is called
with a single argument - the bytes received across the socket - and should
return the bytes to be processed, or <code class="docutils literal notranslate"><span class="pre">None</span></code> to indicate that the bytes should
be discarded. The returned bytes could be the same as the passed in bytes
(e.g. when only verification is done), or they could be completely different
(perhaps if decryption were performed).</p>
<p>To send a configuration to the socket, read in the configuration file and
send it to the socket as a sequence of bytes preceded by a four-byte length
string packed in binary using <code class="docutils literal notranslate"><span class="pre">struct.pack('>L',</span> <span class="pre">n)</span></code>.</p>
<div class="admonition note" id="logging-eval-security">
<p class="admonition-title">Note</p>
<p>Because portions of the configuration are passed through
<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.
While the function only binds to a socket on <code class="docutils literal notranslate"><span class="pre">localhost</span></code>, and so does
not accept connections from remote machines, there are scenarios where
untrusted code could be run under the account of the process which calls
<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
on a multi-user machine where users cannot trust each other, then a
malicious user could arrange to run essentially arbitrary code in a
victim user’s process, simply by connecting to the victim’s
<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
code the attacker wants to have executed in the victim’s process. This is
especially easy to do if the default port is used, but not hard even if a
different port is used. To avoid the risk of this happening, use the
<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
configurations from being applied.</p>
</div>
<div class="versionchanged">
<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>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>If you want to send configurations to the listener which don’t
disable existing loggers, you will need to use a JSON format for
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.
This method allows you to specify <code class="docutils literal notranslate"><span class="pre">disable_existing_loggers</span></code> as
<code class="docutils literal notranslate"><span class="pre">False</span></code> in the configuration you send.</p>
</div>
</dd></dl>
<dl class="py function">
<dt class="sig sig-object py" id="logging.config.stopListening">
<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>
<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>.
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
<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>
</dd></dl>
</section>
<section id="security-considerations">
<h2>Security considerations<a class="headerlink" href="#security-considerations" title="Link to this heading">¶</a></h2>
<p>The logging configuration functionality tries to offer convenience, and in part this
is done by offering the ability to convert text in configuration files into Python
objects used in logging configuration - for example, as described in
<a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>. However, these same mechanisms (importing
callables from user-defined modules and calling them with parameters from the
configuration) could be used to invoke any code you like, and for this reason you
should treat configuration files from untrusted sources with <em>extreme caution</em> and
satisfy yourself that nothing bad can happen if you load them, before actually loading
them.</p>
</section>
<section id="configuration-dictionary-schema">
<span id="logging-config-dictschema"></span><h2>Configuration dictionary schema<a class="headerlink" href="#configuration-dictionary-schema" title="Link to this heading">¶</a></h2>
<p>Describing a logging configuration requires listing the various
objects to create and the connections between them; for example, you
may create a handler named ‘console’ and then say that the logger
named ‘startup’ will send its messages to the ‘console’ handler.
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>
module because you might write your own formatter or handler class.
The parameters to these classes may also need to include external
objects such as <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>. The syntax for describing these
objects and connections is defined in <a class="reference internal" href="#logging-config-dict-connections"><span class="std std-ref">Object connections</span></a>
below.</p>
<section id="dictionary-schema-details">
<h3>Dictionary Schema Details<a class="headerlink" href="#dictionary-schema-details" title="Link to this heading">¶</a></h3>
<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
keys:</p>
<ul class="simple">
<li><p><em>version</em> - to be set to an integer value representing the schema
version. The only valid value at present is 1, but having this key
allows the schema to evolve while still preserving backwards
compatibility.</p></li>
</ul>
<p>All other keys are optional, but if present they will be interpreted
as described below. In all cases below where a ‘configuring dict’ is
mentioned, it will be checked for the special <code class="docutils literal notranslate"><span class="pre">'()'</span></code> key to see if a
custom instantiation is required. If so, the mechanism described in
<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;
otherwise, the context is used to determine what to instantiate.</p>
<ul id="logging-config-dictschema-formatters">
<li><p><em>formatters</em> - the corresponding value will be a dict in which each
key is a formatter id and each value is a dict describing how to
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>
<p>The configuring dict is searched for the following optional keys
which correspond to the arguments passed to create 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">Formatter</span></code></a> object:</p>
<ul class="simple">
<li><p><code class="docutils literal notranslate"><span class="pre">format</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">datefmt</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">style</span></code></p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">validate</span></code> (since version >=3.8)</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">defaults</span></code> (since version >=3.12)</p></li>
</ul>
<p>An optional <code class="docutils literal notranslate"><span class="pre">class</span></code> key indicates the name of the formatter’s
class (as a dotted module and class name). The instantiation
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
most useful for instantiating a customised subclass of
<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
might present exception tracebacks in an expanded or condensed
format. If your formatter requires different or extra configuration
keys, you should use <a class="reference internal" href="#logging-config-dict-userdef"><span class="std std-ref">User-defined objects</span></a>.</p>
</li>
<li><p><em>filters</em> - the corresponding value will be a dict in which each key
is a filter id and each value is a dict describing how to configure
the corresponding Filter instance.</p>
<p>The configuring dict is searched for the key <code class="docutils literal notranslate"><span class="pre">name</span></code> (defaulting to the
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>
instance.</p>
</li>
<li><p><em>handlers</em> - the corresponding value will be a dict in which each
key is a handler id and each value is a dict describing how to
configure the corresponding Handler instance.</p>
<p>The configuring dict is searched for the following keys:</p>
<ul>
<li><p><code class="docutils literal notranslate"><span class="pre">class</span></code> (mandatory). This is the fully qualified name of the
handler class.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">level</span></code> (optional). The level of the handler.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">formatter</span></code> (optional). The id of the formatter for this
handler.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">filters</span></code> (optional). A list of ids of the filters for this
handler.</p>
<div class="versionchanged">
<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>
</div>
</li>
</ul>
<p>All <em>other</em> keys are passed through as keyword arguments to the
handler’s constructor. For example, given the snippet:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>
<span class="w"> </span><span class="nt">console</span><span class="p">:</span>
<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>
<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>
<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>
<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>
<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>
<span class="w"> </span><span class="nt">file</span><span class="p">:</span>
<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>
<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>
<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>
<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>
<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>
</pre></div>
</div>
<p>the handler with id <code class="docutils literal notranslate"><span class="pre">console</span></code> is instantiated as a
<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
stream. The handler with id <code class="docutils literal notranslate"><span class="pre">file</span></code> is instantiated as a
<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
<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>
</li>
<li><p><em>loggers</em> - the corresponding value will be a dict in which each key
is a logger name and each value is a dict describing how to
configure the corresponding Logger instance.</p>
<p>The configuring dict is searched for the following keys:</p>
<ul>
<li><p><code class="docutils literal notranslate"><span class="pre">level</span></code> (optional). The level of the logger.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">propagate</span></code> (optional). The propagation setting of the logger.</p></li>
<li><p><code class="docutils literal notranslate"><span class="pre">filters</span></code> (optional). A list of ids of the filters for this
logger.</p>
<div class="versionchanged">
<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>
</div>
</li>
<li><p><code class="docutils literal notranslate"><span class="pre">handlers</span></code> (optional). A list of ids of the handlers for this
logger.</p></li>
</ul>
<p>The specified loggers will be configured according to the level,
propagation, filters and handlers specified.</p>
</li>
<li><p><em>root</em> - this will be the configuration for the root logger.
Processing of the configuration will be as for any logger, except
that the <code class="docutils literal notranslate"><span class="pre">propagate</span></code> setting will not be applicable.</p></li>
<li><p><em>incremental</em> - whether the configuration is to be interpreted as
incremental to the existing configuration. This value defaults to
<code class="docutils literal notranslate"><span class="pre">False</span></code>, which means that the specified configuration replaces the
existing configuration with the same semantics as used by the
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>
<p>If the specified value is <code class="docutils literal notranslate"><span class="pre">True</span></code>, the configuration is processed
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>
</li>
<li><p><em>disable_existing_loggers</em> - whether any existing non-root loggers are
to be disabled. This setting mirrors the parameter of the same name in
<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>.
This value is ignored if <em>incremental</em> is <code class="docutils literal notranslate"><span class="pre">True</span></code>.</p></li>
</ul>
</section>
<section id="incremental-configuration">
<span id="logging-config-dict-incremental"></span><h3>Incremental Configuration<a class="headerlink" href="#incremental-configuration" title="Link to this heading">¶</a></h3>
<p>It is difficult to provide complete flexibility for incremental
configuration. For example, because objects such as filters
and formatters are anonymous, once a configuration is set up, it is
not possible to refer to such anonymous objects when augmenting a
configuration.</p>
<p>Furthermore, there is not a compelling case for arbitrarily altering
the object graph of loggers, handlers, filters, formatters at
run-time, once a configuration is set up; the verbosity of loggers and
handlers can be controlled just by setting levels (and, in the case of
loggers, propagation flags). Changing the object graph arbitrarily in
a safe way is problematic in a multi-threaded environment; while not
impossible, the benefits are not worth the complexity it adds to the
implementation.</p>
<p>Thus, when the <code class="docutils literal notranslate"><span class="pre">incremental</span></code> key of a configuration dict is present
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
<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>
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
<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>
<p>Using a value in the configuration dict lets configurations to be sent
over the wire as pickled dicts to a socket listener. Thus, the logging
verbosity of a long-running application can be altered over time with
no need to stop and restart the application.</p>
</section>
<section id="object-connections">
<span id="logging-config-dict-connections"></span><h3>Object connections<a class="headerlink" href="#object-connections" title="Link to this heading">¶</a></h3>
<p>The schema describes a set of logging objects - loggers,
handlers, formatters, filters - which are connected to each other in
an object graph. Thus, the schema needs to represent connections
between the objects. For example, say that, once configured, a
particular logger has attached to it a particular handler. For the
purposes of this discussion, we can say that the logger represents the
source, and the handler the destination, of a connection between the
two. Of course in the configured objects this is represented by the
logger holding a reference to the handler. In the configuration dict,
this is done by giving each destination object an id which identifies
it unambiguously, and then using the id in the source object’s
configuration to indicate that a connection exists between the source
and the destination object with that id.</p>
<p>So, for example, consider the following YAML snippet:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">formatters</span><span class="p">:</span>
<span class="w"> </span><span class="nt">brief</span><span class="p">:</span>
<span class="w"> </span><span class="c1"># configuration for formatter with id 'brief' goes here</span>
<span class="w"> </span><span class="nt">precise</span><span class="p">:</span>
<span class="w"> </span><span class="c1"># configuration for formatter with id 'precise' goes here</span>
<span class="nt">handlers</span><span class="p">:</span>
<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>
<span class="w"> </span><span class="c1"># configuration of handler with id 'h1' goes here</span>
<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>
<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>
<span class="w"> </span><span class="c1"># configuration of handler with id 'h2' goes here</span>
<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>
<span class="nt">loggers</span><span class="p">:</span>
<span class="w"> </span><span class="nt">foo.bar.baz</span><span class="p">:</span>
<span class="w"> </span><span class="c1"># other configuration for logger 'foo.bar.baz'</span>
<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>
</pre></div>
</div>
<p>(Note: YAML used here because it’s a little more readable than the
equivalent Python source form for the dictionary.)</p>
<p>The ids for loggers are the logger names which would be used
programmatically to obtain a reference to those loggers, e.g.
<code class="docutils literal notranslate"><span class="pre">foo.bar.baz</span></code>. The ids for Formatters and Filters can be any string
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,
in that they are only meaningful for processing the configuration
dictionary and used to determine connections between objects, and are
not persisted anywhere when the configuration call is complete.</p>
<p>The above snippet indicates that logger named <code class="docutils literal notranslate"><span class="pre">foo.bar.baz</span></code> should
have two handlers attached to it, which are described by the handler
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
<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
<code class="docutils literal notranslate"><span class="pre">precise</span></code>.</p>
</section>
<section id="user-defined-objects">
<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>
<p>The schema supports user-defined objects for handlers, filters and
formatters. (Loggers do not need to have different types for
different instances, so there is no support in this configuration
schema for user-defined logger classes.)</p>
<p>Objects to be configured are described by dictionaries
which detail their configuration. In some places, the logging system
will be able to infer from the context how an object is to be
instantiated, but when a user-defined object is to be instantiated,
the system will not know how to do this. In order to provide complete
flexibility for user-defined object instantiation, the user needs
to provide a ‘factory’ - a callable which is called with a
configuration dictionary and which returns the instantiated object.
This is signalled by an absolute import path to the factory being
made available under the special key <code class="docutils literal notranslate"><span class="pre">'()'</span></code>. Here’s a concrete
example:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">formatters</span><span class="p">:</span>
<span class="w"> </span><span class="nt">brief</span><span class="p">:</span>
<span class="w"> </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s">'%(message)s'</span>
<span class="w"> </span><span class="nt">default</span><span class="p">:</span>
<span class="w"> </span><span class="nt">format</span><span class="p">:</span><span class="w"> </span><span class="s">'%(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'</span>
<span class="w"> </span><span class="nt">datefmt</span><span class="p">:</span><span class="w"> </span><span class="s">'%Y-%m-%d</span><span class="nv"> </span><span class="s">%H:%M:%S'</span>
<span class="w"> </span><span class="nt">custom</span><span class="p">:</span>
<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>
<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>
<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>
<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>
</pre></div>
</div>
<p>The above YAML snippet defines three formatters. The first, with id
<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
specified format string. The second, with id <code class="docutils literal notranslate"><span class="pre">default</span></code>, has a
longer format and also defines the time format explicitly, and will
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
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>
formatters have configuration sub-dictionaries:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="s1">'format'</span> <span class="p">:</span> <span class="s1">'</span><span class="si">%(message)s</span><span class="s1">'</span>
<span class="p">}</span>
</pre></div>
</div>
<p>and:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="s1">'format'</span> <span class="p">:</span> <span class="s1">'</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">'</span><span class="p">,</span>
<span class="s1">'datefmt'</span> <span class="p">:</span> <span class="s1">'%Y-%m-</span><span class="si">%d</span><span class="s1"> %H:%M:%S'</span>
<span class="p">}</span>
</pre></div>
</div>
<p>respectively, and as these dictionaries do not contain the special key
<code class="docutils literal notranslate"><span class="pre">'()'</span></code>, the instantiation is inferred from the context: as a result,
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
configuration sub-dictionary for the third formatter, with id
<code class="docutils literal notranslate"><span class="pre">custom</span></code>, is:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="s1">'()'</span> <span class="p">:</span> <span class="s1">'my.package.customFormatterFactory'</span><span class="p">,</span>
<span class="s1">'bar'</span> <span class="p">:</span> <span class="s1">'baz'</span><span class="p">,</span>
<span class="s1">'spam'</span> <span class="p">:</span> <span class="mf">99.9</span><span class="p">,</span>
<span class="s1">'answer'</span> <span class="p">:</span> <span class="mi">42</span>
<span class="p">}</span>
</pre></div>
</div>
<p>and this contains the special key <code class="docutils literal notranslate"><span class="pre">'()'</span></code>, which means that
user-defined instantiation is wanted. In this case, the specified
factory callable will be used. If it is an actual callable it will be
used directly - otherwise, if you specify a string (as in the example)
the actual callable will be located using normal import mechanisms.
The callable will be called with the <strong>remaining</strong> items in the
configuration sub-dictionary as keyword arguments. In the above
example, the formatter with id <code class="docutils literal notranslate"><span class="pre">custom</span></code> will be assumed to be
returned by the call:</p>
<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">'baz'</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>
</pre></div>
</div>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<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
the above example should not be configuration dictionaries or references such
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
configuration machinery, but passed to the callable as-is.</p>
</div>
<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
valid keyword parameter name, and so will not clash with the names of
the keyword arguments used in the call. The <code class="docutils literal notranslate"><span class="pre">'()'</span></code> also serves as a
mnemonic that the corresponding value is a callable.</p>
<div class="versionchanged">
<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
filter instances in addition to ids.</p>
</div>
<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
mapping of attribute names to values. If found, the specified attributes will
be set on the user-defined object before it is returned. Thus, with the
following configuration:</p>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="p">{</span>
<span class="s1">'()'</span> <span class="p">:</span> <span class="s1">'my.package.customFormatterFactory'</span><span class="p">,</span>
<span class="s1">'bar'</span> <span class="p">:</span> <span class="s1">'baz'</span><span class="p">,</span>
<span class="s1">'spam'</span> <span class="p">:</span> <span class="mf">99.9</span><span class="p">,</span>
<span class="s1">'answer'</span> <span class="p">:</span> <span class="mi">42</span><span class="p">,</span>
<span class="s1">'.'</span> <span class="p">{</span>
<span class="s1">'foo'</span><span class="p">:</span> <span class="s1">'bar'</span><span class="p">,</span>
<span class="s1">'baz'</span><span class="p">:</span> <span class="s1">'bozz'</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
<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
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>
<div class="admonition warning">
<p class="admonition-title">Warning</p>
<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
the above example should not be configuration dictionaries or references such
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
configuration machinery, but set as attribute values as-is.</p>
</div>
</section>
<section id="handler-configuration-order">
<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>
<p>Handlers are configured in alphabetical order of their keys, and a configured
handler replaces the configuration dictionary in (a working copy of) the
<code class="docutils literal notranslate"><span class="pre">handlers</span></code> dictionary in the schema. If you use a construct such as
<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
configuration dictionary for the handler named <code class="docutils literal notranslate"><span class="pre">foo</span></code>, and later (once that
handler has been configured) it points to the configured handler instance.
Thus, <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code> could resolve to either a dictionary or a handler
instance. In general, it is wise to name handlers in a way such that dependent
handlers are configured _after_ any handlers they depend on; that allows
something like <code class="docutils literal notranslate"><span class="pre">cfg://handlers.foo</span></code> to be used in configuring a handler that
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>,
problems would result, because the configuration of <code class="docutils literal notranslate"><span class="pre">bar</span></code> would be attempted
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.
However, if the dependent handler were named <code class="docutils literal notranslate"><span class="pre">foobar</span></code>, it would be configured
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
configured handler <code class="docutils literal notranslate"><span class="pre">foo</span></code>, and not its configuration dictionary.</p>
</section>
<section id="access-to-external-objects">
<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>
<p>There are times where a configuration needs to refer to objects
external to the configuration, for example <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code>. If the
configuration dict is constructed using Python code, this is
straightforward, but a problem arises when the configuration is
provided via a text file (e.g. JSON, YAML). In a text file, there is
no standard way to distinguish <code class="docutils literal notranslate"><span class="pre">sys.stderr</span></code> from the literal string
<code class="docutils literal notranslate"><span class="pre">'sys.stderr'</span></code>. To facilitate this distinction, the configuration
system looks for certain special prefixes in string values and
treat them specially. For example, if the literal string
<code class="docutils literal notranslate"><span class="pre">'ext://sys.stderr'</span></code> is provided as a value in the configuration,
then the <code class="docutils literal notranslate"><span class="pre">ext://</span></code> will be stripped off and the remainder of the
value processed using normal import mechanisms.</p>
<p>The handling of such prefixes is done in a way analogous to protocol
handling: there is a generic mechanism to look for prefixes which
match the regular expression <code class="docutils literal notranslate"><span class="pre">^(?P<prefix>[a-z]+)://(?P<suffix>.*)$</span></code>
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
in a prefix-dependent manner and the result of the processing replaces
the string value. If the prefix is not recognised, then the string
value will be left as-is.</p>
</section>
<section id="access-to-internal-objects">
<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>
<p>As well as external objects, there is sometimes also a need to refer
to objects in the configuration. This will be done implicitly by the
configuration system for things that it knows about. For example, the
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
automatically be converted to the value <code class="docutils literal notranslate"><span class="pre">logging.DEBUG</span></code>, and the
<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
object id and resolve to the appropriate destination object.</p>
<p>However, a more generic mechanism is needed for user-defined
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
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
a <code class="docutils literal notranslate"><span class="pre">target</span></code> argument which is another handler to delegate to. Since
the system already knows about this class, then in the configuration,
the given <code class="docutils literal notranslate"><span class="pre">target</span></code> just needs to be the object id of the relevant
target handler, and the system will resolve to the handler from the
id. If, however, a user defines a <code class="docutils literal notranslate"><span class="pre">my.package.MyHandler</span></code> which has
an <code class="docutils literal notranslate"><span class="pre">alternate</span></code> handler, the configuration system would not know that
the <code class="docutils literal notranslate"><span class="pre">alternate</span></code> referred to a handler. To cater for this, a generic
resolution system allows the user to specify:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>
<span class="w"> </span><span class="nt">file</span><span class="p">:</span>
<span class="w"> </span><span class="c1"># configuration of file handler goes here</span>
<span class="w"> </span><span class="nt">custom</span><span class="p">:</span>
<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>
<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>
</pre></div>
</div>
<p>The literal string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.file'</span></code> will be resolved in an
analogous way to strings with the <code class="docutils literal notranslate"><span class="pre">ext://</span></code> prefix, but looking
in the configuration itself rather than the import namespace. The
mechanism allows access by dot or by index, in a similar way to
that provided by <code class="docutils literal notranslate"><span class="pre">str.format</span></code>. Thus, given the following snippet:</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>
<span class="w"> </span><span class="nt">email</span><span class="p">:</span>
<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>
<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>
<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>
<span class="w"> </span><span class="nt">toaddrs</span><span class="p">:</span>
<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>
<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>
<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>
</pre></div>
</div>
<p>in the configuration, the string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers'</span></code> would resolve to
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>
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,
and so on. The string <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.toaddrs[1]</span></code> would
resolve to <code class="docutils literal notranslate"><span class="pre">'dev_team@domain.tld'</span></code> and the string
<code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.toaddrs[0]'</span></code> would resolve to the value
<code class="docutils literal notranslate"><span class="pre">'support_team@domain.tld'</span></code>. The <code class="docutils literal notranslate"><span class="pre">subject</span></code> value could be accessed
using either <code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email.subject'</span></code> or, equivalently,
<code class="docutils literal notranslate"><span class="pre">'cfg://handlers.email[subject]'</span></code>. The latter form only needs to be
used if the key contains spaces or non-alphanumeric characters. Please note
that the characters <code class="docutils literal notranslate"><span class="pre">[</span></code> and <code class="docutils literal notranslate"><span class="pre">]</span></code> are not allowed in the keys. If an
index value consists only of decimal digits, access will be attempted
using the corresponding integer value, falling back to the string
value if needed.</p>
<p>Given a string <code class="docutils literal notranslate"><span class="pre">cfg://handlers.myhandler.mykey.123</span></code>, this will
resolve to <code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey']['123']</span></code>.
If the string is specified as <code class="docutils literal notranslate"><span class="pre">cfg://handlers.myhandler.mykey[123]</span></code>,
the system will attempt to retrieve the value from
<code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey'][123]</span></code>, and fall back
to <code class="docutils literal notranslate"><span class="pre">config_dict['handlers']['myhandler']['mykey']['123']</span></code> if that
fails.</p>
</section>
<section id="import-resolution-and-custom-importers">
<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>
<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
to do its importing. You may want to replace this with your own importing
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
<code class="xref py py-class docutils literal notranslate"><span class="pre">DictConfigurator</span></code> or its superclass, the
<code class="xref py py-class docutils literal notranslate"><span class="pre">BaseConfigurator</span></code> class. However, you need to be
careful because of the way functions are accessed from classes via
descriptors. If you are using a Python callable to do your imports, and you
want to define it at class level rather than instance level, you need to wrap
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>
<div class="highlight-python3 notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span><span class="w"> </span><span class="nn">importlib</span><span class="w"> </span><span class="kn">import</span> <span class="n">import_module</span>
<span class="kn">from</span><span class="w"> </span><span class="nn">logging.config</span><span class="w"> </span><span class="kn">import</span> <span class="n">BaseConfigurator</span>
<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>
</pre></div>
</div>
<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
callable on a configurator <em>instance</em>.</p>
</section>
<section id="configuring-queuehandler-and-queuelistener">
<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>
<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
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
can configure both together. After the configuration, the <code class="docutils literal notranslate"><span class="pre">QueueListener</span></code> instance
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
the created handler, and that in turn will be available to you using
<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
<code class="docutils literal notranslate"><span class="pre">QueueHandler</span></code> in your configuration. The dictionary schema for configuring the pair
is shown in the example YAML snippet below.</p>
<div class="highlight-yaml notranslate"><div class="highlight"><pre><span></span><span class="nt">handlers</span><span class="p">:</span>
<span class="w"> </span><span class="nt">qhand</span><span class="p">:</span>
<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>
<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>
<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>
<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="w"> </span><span class="l l-Scalar l-Scalar-Plain">hand_name_1</span>
<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>
<span class="w"> </span><span class="l l-Scalar l-Scalar-Plain">...</span>
</pre></div>
</div>
<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>
<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>
<ul>
<li><p>An object implementing the <a class="reference internal" href="queue.html#queue.Queue.put_nowait" title="queue.Queue.put_nowait"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Queue.put_nowait</span></code></a>
and <a class="reference internal" href="queue.html#queue.Queue.get" title="queue.Queue.get"><code class="xref py py-meth docutils literal notranslate"><span class="pre">Queue.get</span></code></a> public API. For instance, this may be
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, or a proxy
obtained by <a class="reference internal" href="multiprocessing.html#multiprocessing.managers.SyncManager.Queue" title="multiprocessing.managers.SyncManager.Queue"><code class="xref py py-meth docutils literal notranslate"><span class="pre">multiprocessing.managers.SyncManager.Queue()</span></code></a>.</p>
<p>This is of course only possible if you are constructing or modifying
the configuration dictionary in code.</p>
</li>
<li><p>A string that resolves to a callable which, when called with no arguments, returns
the queue instance to use. That callable could be a <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,
such as <code class="docutils literal notranslate"><span class="pre">my.module.queue_factory()</span></code>.</p></li>
<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
<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
<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>
</ul>
<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
created and used.</p>
<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>
<ul class="simple">
<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
possible if you are constructing or modifying the configuration dictionary in
code.</p></li>
<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
<code class="docutils literal notranslate"><span class="pre">'my.package.CustomListener'</span></code>.</p></li>
<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
<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
callable with the same signature as the <code class="docutils literal notranslate"><span class="pre">QueueListener</span></code> initializer.</p></li>
</ul>
<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>
<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
configuration (not shown in the above snippet) which will be passed to the queue
listener.</p>
<p>Any custom queue handler and listener classes will need to be defined with the same
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
<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>
<div class="versionadded">
<p><span class="versionmodified added">Added in version 3.12.</span></p>
</div>
</section>
</section>
<section id="configuration-file-format">
<span id="logging-config-fileformat"></span><h2>Configuration file format<a class="headerlink" href="#configuration-file-format" title="Link to this heading">¶</a></h2>
<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
<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
<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
entities of each type which are defined in the file. For each such entity, there
is a separate section which identifies how that entity is configured. Thus, for
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
configuration details are held in a section <code class="docutils literal notranslate"><span class="pre">[logger_log01]</span></code>. Similarly, a
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
configuration held in a section called <code class="docutils literal notranslate"><span class="pre">[handler_hand01]</span></code>, while a formatter
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
specified in a section called <code class="docutils literal notranslate"><span class="pre">[formatter_form01]</span></code>. The root logger
configuration must be specified in a section called <code class="docutils literal notranslate"><span class="pre">[logger_root]</span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<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
not provide functionality to cover certain aspects of logging. For example,
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
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>.
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
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
enhancements to configuration functionality will be added 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>, so it’s worth considering transitioning to this newer
API when it’s convenient to do so.</p>
</div>
<p>Examples of these sections in the file are given below.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[loggers]</span>
<span class="na">keys</span><span class="o">=</span><span class="s">root,log02,log03,log04,log05,log06,log07</span>
<span class="k">[handlers]</span>
<span class="na">keys</span><span class="o">=</span><span class="s">hand01,hand02,hand03,hand04,hand05,hand06,hand07,hand08,hand09</span>
<span class="k">[formatters]</span>
<span class="na">keys</span><span class="o">=</span><span class="s">form01,form02,form03,form04,form05,form06,form07,form08,form09</span>
</pre></div>
</div>
<p>The root logger must specify a level and a list of handlers. An example of a
root logger section is given below.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[logger_root]</span>
<span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>
<span class="na">handlers</span><span class="o">=</span><span class="s">hand01</span>
</pre></div>
</div>
<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
<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
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>
package’s namespace.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">handlers</span></code> entry is a comma-separated list of handler names, which must
appear in the <code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> section. These names must appear in the
<code class="docutils literal notranslate"><span class="pre">[handlers]</span></code> section and have corresponding sections in the configuration
file.</p>
<p>For loggers other than the root logger, some additional information is required.
This is illustrated by the following example.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[logger_parser]</span>
<span class="na">level</span><span class="o">=</span><span class="s">DEBUG</span>
<span class="na">handlers</span><span class="o">=</span><span class="s">hand01</span>
<span class="na">propagate</span><span class="o">=</span><span class="s">1</span>
<span class="na">qualname</span><span class="o">=</span><span class="s">compiler.parser</span>
</pre></div>
</div>
<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,
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
consults loggers higher up the hierarchy to determine the effective level of the
logger. The <code class="docutils literal notranslate"><span class="pre">propagate</span></code> entry is set to 1 to indicate that messages must
propagate to handlers higher up the logger hierarchy from this logger, or 0 to
indicate that messages are <strong>not</strong> propagated to handlers up the hierarchy. The
<code class="docutils literal notranslate"><span class="pre">qualname</span></code> entry is the hierarchical channel name of the logger, that is to
say the name used by the application to get the logger.</p>
<p>Sections which specify handler configuration are exemplified by the following.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[handler_hand01]</span>
<span class="na">class</span><span class="o">=</span><span class="s">StreamHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form01</span>
<span class="na">args</span><span class="o">=</span><span class="s">(sys.stdout,)</span>
</pre></div>
</div>
<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>
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
loggers, and <code class="docutils literal notranslate"><span class="pre">NOTSET</span></code> is taken to mean ‘log everything’.</p>
<p>The <code class="docutils literal notranslate"><span class="pre">formatter</span></code> entry indicates the key name of the formatter for this
handler. If blank, a default formatter (<code class="docutils literal notranslate"><span class="pre">logging._defaultFormatter</span></code>) is used.
If a name is specified, it must appear in the <code class="docutils literal notranslate"><span class="pre">[formatters]</span></code> section and have
a corresponding section in the configuration file.</p>
<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>
package’s namespace, is the list of arguments to the constructor for the handler
class. Refer to the constructors for the relevant handlers, or to the examples
below, to see how typical entries are constructed. If not provided, it defaults
to <code class="docutils literal notranslate"><span class="pre">()</span></code>.</p>
<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
<code class="docutils literal notranslate"><span class="pre">logging</span></code> package’s namespace, is the keyword argument dict to the constructor
for the handler class. If not provided, it defaults to <code class="docutils literal notranslate"><span class="pre">{}</span></code>.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[handler_hand02]</span>
<span class="na">class</span><span class="o">=</span><span class="s">FileHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">DEBUG</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form02</span>
<span class="na">args</span><span class="o">=</span><span class="s">('python.log', 'w')</span>
<span class="k">[handler_hand03]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.SocketHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">INFO</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form03</span>
<span class="na">args</span><span class="o">=</span><span class="s">('localhost', handlers.DEFAULT_TCP_LOGGING_PORT)</span>
<span class="k">[handler_hand04]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.DatagramHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">WARN</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form04</span>
<span class="na">args</span><span class="o">=</span><span class="s">('localhost', handlers.DEFAULT_UDP_LOGGING_PORT)</span>
<span class="k">[handler_hand05]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.SysLogHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">ERROR</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form05</span>
<span class="na">args</span><span class="o">=</span><span class="s">(('localhost', handlers.SYSLOG_UDP_PORT), handlers.SysLogHandler.LOG_USER)</span>
<span class="k">[handler_hand06]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.NTEventLogHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">CRITICAL</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form06</span>
<span class="na">args</span><span class="o">=</span><span class="s">('Python Application', '', 'Application')</span>
<span class="k">[handler_hand07]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.SMTPHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">WARN</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form07</span>
<span class="na">args</span><span class="o">=</span><span class="s">('localhost', 'from@abc', ['user1@abc', 'user2@xyz'], 'Logger Subject')</span>
<span class="na">kwargs</span><span class="o">=</span><span class="s">{'timeout': 10.0}</span>
<span class="k">[handler_hand08]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.MemoryHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form08</span>
<span class="na">target</span><span class="o">=</span>
<span class="na">args</span><span class="o">=</span><span class="s">(10, ERROR)</span>
<span class="k">[handler_hand09]</span>
<span class="na">class</span><span class="o">=</span><span class="s">handlers.HTTPHandler</span>
<span class="na">level</span><span class="o">=</span><span class="s">NOTSET</span>
<span class="na">formatter</span><span class="o">=</span><span class="s">form09</span>
<span class="na">args</span><span class="o">=</span><span class="s">('localhost:9022', '/log', 'GET')</span>
<span class="na">kwargs</span><span class="o">=</span><span class="s">{'secure': True}</span>
</pre></div>
</div>
<p>Sections which specify formatter configuration are typified by the following.</p>
<div class="highlight-ini notranslate"><div class="highlight"><pre><span></span><span class="k">[formatter_form01]</span>
<span class="na">format</span><span class="o">=</span><span class="s">F1 %(asctime)s %(levelname)s %(message)s %(customfield)s</span>
<span class="na">datefmt</span><span class="o">=</span>
<span class="na">style</span><span class="o">=</span><span class="s">%</span>
<span class="na">validate</span><span class="o">=</span><span class="s">True</span>
<span class="na">defaults={'customfield'</span><span class="o">:</span><span class="w"> </span><span class="s">'defaultvalue'</span><span class="na">}</span>
<span class="na">class</span><span class="o">=</span><span class="s">logging.Formatter</span>
</pre></div>
</div>
<p>The arguments for the formatter configuration are the same as the keys
in the dictionary schema <a class="reference internal" href="#logging-config-dictschema-formatters"><span class="std std-ref">formatters section</span></a>.</p>
<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
the <code class="docutils literal notranslate"><span class="pre">logging</span></code> package’s namespace, is a dictionary of default values for
custom formatting fields. If not provided, it defaults to <code class="docutils literal notranslate"><span class="pre">None</span></code>.</p>
<div class="admonition note">
<p class="admonition-title">Note</p>
<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
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
and receive configurations via sockets. The risks are limited to where
multiple users with no mutual trust run code on the same machine; see 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> documentation for more information.</p>
</div>
<div class="admonition seealso">
<p class="admonition-title">See also</p>
<dl class="simple">
<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>
</dd>
<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>
</dd>
</dl>
</div>
</section>
</section>
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<h3><a href="../contents.html">Table of Contents</a></h3>
<ul>
<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>
<li><a class="reference internal" href="#configuration-functions">Configuration functions</a></li>
<li><a class="reference internal" href="#security-considerations">Security considerations</a></li>
<li><a class="reference internal" href="#configuration-dictionary-schema">Configuration dictionary schema</a><ul>
<li><a class="reference internal" href="#dictionary-schema-details">Dictionary Schema Details</a></li>
<li><a class="reference internal" href="#incremental-configuration">Incremental Configuration</a></li>
<li><a class="reference internal" href="#object-connections">Object connections</a></li>
<li><a class="reference internal" href="#user-defined-objects">User-defined objects</a></li>
<li><a class="reference internal" href="#handler-configuration-order">Handler configuration order</a></li>
<li><a class="reference internal" href="#access-to-external-objects">Access to external objects</a></li>
<li><a class="reference internal" href="#access-to-internal-objects">Access to internal objects</a></li>
<li><a class="reference internal" href="#import-resolution-and-custom-importers">Import resolution and custom importers</a></li>
<li><a class="reference internal" href="#configuring-queuehandler-and-queuelistener">Configuring QueueHandler and QueueListener</a></li>
</ul>
</li>
<li><a class="reference internal" href="#configuration-file-format">Configuration file format</a></li>
</ul>
</li>
</ul>
</div>
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<h4>Previous topic</h4>
<p class="topless"><a href="logging.html"
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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<p class="topless"><a href="logging.handlers.html"
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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