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<li>Logging system</li>
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<div class="section" id="logging-system">
<h1>Logging system<a class="headerlink" href="#logging-system" title="Permalink to this headline">¶</a></h1>
<div class="section" id="overview">
<h2>Overview<a class="headerlink" href="#overview" title="Permalink to this headline">¶</a></h2>
<p>The Astropy logging system is designed to give users flexibility in deciding
which log messages to show, to capture them, and to send them to a file.</p>
<p>All messages printed by Astropy routines should use the built-in logging
facility (normal <tt class="docutils literal"><span class="pre">print()</span></tt> calls should only be done by routines that are
explicitly requested to print output). Messages can have one of several
levels:</p>
<ul class="simple">
<li>DEBUG: Detailed information, typically of interest only when diagnosing
problems.</li>
<li>INFO: An message conveying information about the current task, and
confirming that things are working as expected</li>
<li>WARNING: An indication that something unexpected happened, and that user
action may be required.</li>
<li>ERROR: indicates a more serious issue, including exceptions</li>
</ul>
<p>By default, only WARNING and ERROR messages are displayed, and are sent to a
log file located at <tt class="docutils literal"><span class="pre">~/.astropy/astropy.log</span></tt> (if the file is writeable).</p>
</div>
<div class="section" id="configuring-the-logging-system">
<h2>Configuring the logging system<a class="headerlink" href="#configuring-the-logging-system" title="Permalink to this headline">¶</a></h2>
<p>First, import the logger:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">log</span>
</pre></div>
</div>
<p>The threshold level (defined above) for messages can be set with e.g.:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">setLevel</span><span class="p">(</span><span class="s">'INFO'</span><span class="p">)</span>
</pre></div>
</div>
<p>Color (enabled by default) can be disabled with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">setColor</span><span class="p">(</span><span class="bp">False</span><span class="p">)</span>
</pre></div>
</div>
<p>Warnings from <tt class="docutils literal"><span class="pre">warnings.warn</span></tt> can be logged with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">enable_warnings_logging</span><span class="p">()</span>
</pre></div>
</div>
<p>which can be disabled with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">disable_warnings_logging</span><span class="p">()</span>
</pre></div>
</div>
<p>and exceptions can be included in the log with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">set_exception_logging</span><span class="p">()</span>
</pre></div>
</div>
<p>which can be disabled with:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="n">log</span><span class="o">.</span><span class="n">disable_exception_logging</span><span class="p">()</span>
</pre></div>
</div>
<p>It is also possible to set these settings from the Astropy configuration file,
which also allows an overall log file to be specified. See
<a class="reference internal" href="#using-the-configuration-file">Using the configuration file</a> for more information.</p>
</div>
<div class="section" id="context-managers">
<h2>Context managers<a class="headerlink" href="#context-managers" title="Permalink to this headline">¶</a></h2>
<p>In some cases, you may want to capture the log messages, for example to check
whether a specific message was output, or to log the messages from a specific
section of code to a file. Both of these are possible using context managers.</p>
<p>To add the log messages to a list, first import the logger if you have not
already done so:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="kn">from</span> <span class="nn">astropy</span> <span class="kn">import</span> <span class="n">log</span>
</pre></div>
</div>
<p>then enclose the code in which you want to log the messages to a list in a
<tt class="docutils literal"><span class="pre">with</span></tt> statement:</p>
<div class="highlight-python"><pre>with log.log_to_list() as log_list:
# your code here</pre>
</div>
<p>In the above example, once the block of code has executed, <tt class="docutils literal"><span class="pre">log_list</span></tt> will
be a Python list containing all the Astropy logging messages that were raised.
Note that messages continue to be output as normal.</p>
<p>Similarly, you can output the log messages of a specific section of code to a
file using:</p>
<div class="highlight-python"><pre>with log.log_to_file('myfile.log'):
# your code here</pre>
</div>
<p>which will add all the messages to <tt class="docutils literal"><span class="pre">myfile.log</span></tt> (this is in addition to the
overall log file mentioned in <a class="reference internal" href="#using-the-configuration-file">Using the configuration file</a>).</p>
<p>While these context managers will include all the messages emitted by the
logger (using the global level set by <tt class="docutils literal"><span class="pre">log.setLevel</span></tt>), it is possible to
filter a subset of these using <tt class="docutils literal"><span class="pre">filter_level=</span></tt>, and specifying one of
<tt class="docutils literal"><span class="pre">'DEBUG'</span></tt>, <tt class="docutils literal"><span class="pre">'INFO'</span></tt>, <tt class="docutils literal"><span class="pre">'WARN'</span></tt>, <tt class="docutils literal"><span class="pre">'ERROR'</span></tt>. Note that if
<tt class="docutils literal"><span class="pre">filter_level</span></tt> is a lower level than that set via <tt class="docutils literal"><span class="pre">setLevel</span></tt>, only
messages with the level set by <tt class="docutils literal"><span class="pre">setLevel</span></tt> or higher will be included (i.e.
<tt class="docutils literal"><span class="pre">filter_level</span></tt> is only filtering a subset of the messages normally emitted
by the logger).</p>
<p>Similarly, it is possible to filter a subset of the messages by origin by
specifying <tt class="docutils literal"><span class="pre">filter_origin=</span></tt> followed by a string. If the origin of a message
starts with that string, the message will be included in the context manager.
For example, <tt class="docutils literal"><span class="pre">filter_origin='astropy.wcs'</span></tt> will include only messages
emitted in the <tt class="docutils literal"><span class="pre">astropy.wcs</span></tt> sub-package.</p>
</div>
<div class="section" id="using-the-configuration-file">
<h2>Using the configuration file<a class="headerlink" href="#using-the-configuration-file" title="Permalink to this headline">¶</a></h2>
<p>Options for the logger can be set in the <tt class="docutils literal"><span class="pre">[config.logging_helper]</span></tt> section
of the Astropy configuration file:</p>
<div class="highlight-python"><div class="highlight"><pre><span class="p">[</span><span class="n">config</span><span class="o">.</span><span class="n">logging_helper</span><span class="p">]</span>
<span class="c"># Threshold for the logging messages. Logging messages that are less severe</span>
<span class="c"># than this level will be ignored. The levels are 'DEBUG', 'INFO', 'WARNING',</span>
<span class="c"># 'ERROR'</span>
<span class="n">log_level</span> <span class="o">=</span> <span class="s">'INFO'</span>
<span class="c"># Whether to use color for the level names</span>
<span class="n">use_color</span> <span class="o">=</span> <span class="bp">True</span>
<span class="c"># Whether to log warnings.warn calls</span>
<span class="n">log_warnings</span> <span class="o">=</span> <span class="bp">False</span>
<span class="c"># Whether to log exceptions before raising them</span>
<span class="n">log_exceptions</span> <span class="o">=</span> <span class="bp">False</span>
<span class="c"># Whether to always log messages to a log file</span>
<span class="n">log_to_file</span> <span class="o">=</span> <span class="bp">True</span>
<span class="c"># The file to log messages to</span>
<span class="n">log_file_path</span> <span class="o">=</span> <span class="s">'~/.astropy/astropy.log'</span>
<span class="c"># Threshold for logging messages to log_file_path</span>
<span class="n">log_file_level</span> <span class="o">=</span> <span class="s">'INFO'</span>
<span class="c"># Format for log file entries</span>
<span class="n">log_file_format</span> <span class="o">=</span> <span class="s">'</span><span class="si">%(asctime)s</span><span class="s">, </span><span class="si">%(origin)s</span><span class="s">, </span><span class="si">%(levelname)s</span><span class="s">, </span><span class="si">%(message)s</span><span class="s">'</span>
</pre></div>
</div>
</div>
<div class="section" id="reference-api">
<h2>Reference/API<a class="headerlink" href="#reference-api" title="Permalink to this headline">¶</a></h2>
<div class="section" id="module-astropy.logger">
<span id="astropy-logger-module"></span><h3>astropy.logger Module<a class="headerlink" href="#module-astropy.logger" title="Permalink to this headline">¶</a></h3>
<p>This module defines a logging class based on the built-in logging module</p>
<div class="section" id="classes">
<h4>Classes<a class="headerlink" href="#classes" title="Permalink to this headline">¶</a></h4>
<table border="1" class="longtable docutils">
<colgroup>
<col width="10%" />
<col width="90%" />
</colgroup>
<tbody valign="top">
<tr class="row-odd"><td><a class="reference internal" href="_generated/astropy.logger.AstropyLogger.html#astropy.logger.AstropyLogger" title="astropy.logger.AstropyLogger"><tt class="xref py py-obj docutils literal"><span class="pre">AstropyLogger</span></tt></a>(name[, level])</td>
<td>This class is used to set up the Astropy logging.</td>
</tr>
<tr class="row-even"><td><a class="reference internal" href="_generated/astropy.logger.LoggingError.html#astropy.logger.LoggingError" title="astropy.logger.LoggingError"><tt class="xref py py-obj docutils literal"><span class="pre">LoggingError</span></tt></a></td>
<td>This exception is for various errors that occur in the astropy logger, typically when activating or deactivating logger-related features.</td>
</tr>
</tbody>
</table>
</div>
</div>
</div>
</div>
</div>
</div>
</div>
<div class="sphinxsidebar">
<div class="sphinxsidebarwrapper"><h3>Page Contents</h3>
<ul>
<li><a class="reference internal" href="#">Logging system</a><ul>
<li><a class="reference internal" href="#overview">Overview</a></li>
<li><a class="reference internal" href="#configuring-the-logging-system">Configuring the logging system</a></li>
<li><a class="reference internal" href="#context-managers">Context managers</a></li>
<li><a class="reference internal" href="#using-the-configuration-file">Using the configuration file</a></li>
<li><a class="reference internal" href="#reference-api">Reference/API</a><ul>
<li><a class="reference internal" href="#module-astropy.logger">astropy.logger Module</a><ul>
<li><a class="reference internal" href="#classes">Classes</a><ul>
</ul>
</li>
</ul>
</li>
</ul>
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