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POPython logging: Why is __init__ called twice?
 

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  1. POPython logging: Why is __init__ called twice?
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    <p>I am trying to use python logging with a config file and an own handler. This works to some degree. What really puzzle me is <code>__init__</code> being called twice and <code>__del__</code> being called once. When I remove the whole config file stuff and create the handler directly within the code <code>__init__</code> is called once and <code>__del__</code> is never called.</p> <p>My questions:</p> <ol> <li>Why is <code>__init__</code> called twice?</li> <li>Why is <code>__del__</code> called less often than <code>__init__</code>?</li> </ol> <p>The code:</p> <pre><code>#!/bin/env python import logging import logging.handlers import logging.config class Test1TimedRotatingFileHandler(logging.handlers.TimedRotatingFileHandler): def __init__(self,filename): print "init called" logging.handlers.TimedRotatingFileHandler.__init__(self,filename, when='S', interval=86400, backupCount=8, encoding=None) def __del__(self): print "del called" if hasattr(logging.handlers.TimedRotatingFileHandler,"__del__"): logging.handlers.TimedRotatingFileHandler.__del__(self) logging.config.fileConfig('/root/test1.conf') logger = logging.getLogger("test1") </code></pre> <p>The config file:</p> <pre><code>[formatters] keys: simple [handlers] keys: file [loggers] keys: root [formatter_simple] format: "%(message)s" [handler_file] class: test1.Test1TimedRotatingFileHandler args: ("/root/test1.log",) level=INFO [logger_root] level: INFO handlers: file qualname: test1 </code></pre> <p>Output looks like this:</p> <pre><code>init called init called del called </code></pre> <p>Using the debugger to get the stack trace as suggested by Sentinal reveals this:</p> <p>First call:</p> <pre><code>&gt; /root/test1.py(12)__init__() -&gt; print "init called" (Pdb) where /root/test1.py(21)&lt;module&gt;() -&gt; logging.config.fileConfig('/root/test1.conf') /usr/local/python/2.6.4/lib/python2.6/logging/config.py(84)fileConfig() -&gt; handlers = _install_handlers(cp, formatters) /usr/local/python/2.6.4/lib/python2.6/logging/config.py(156)_install_handlers() -&gt; klass = _resolve(klass) /usr/local/python/2.6.4/lib/python2.6/logging/config.py(94)_resolve() -&gt; found = __import__(used) /root/test1.py(21)&lt;module&gt;() -&gt; logging.config.fileConfig('/root/test1.conf') /usr/local/python/2.6.4/lib/python2.6/logging/config.py(84)fileConfig() -&gt; handlers = _install_handlers(cp, formatters) /usr/local/python/2.6.4/lib/python2.6/logging/config.py(159)_install_handlers() -&gt; h = klass(*args) &gt; /root/test1.py(12)__init__() -&gt; print "init called" (Pdb) c init called </code></pre> <p>Second call:</p> <pre><code>&gt; /root/test1.py(12)__init__() -&gt; print "init called" (Pdb) w /root/test1.py(21)&lt;module&gt;() -&gt; logging.config.fileConfig('/root/test1.conf') /usr/local/python/2.6.4/lib/python2.6/logging/config.py(84)fileConfig() -&gt; handlers = _install_handlers(cp, formatters) /usr/local/python/2.6.4/lib/python2.6/logging/config.py(159)_install_handlers() -&gt; h = klass(*args) &gt; /root/test1.py(12)__init__() -&gt; print "init called" </code></pre>
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    1. CO"""Why is init called twice?""" - take the debugger and check why it is called twice. Looking at the call stack can be helpful...
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