title: Finding a list of all double-underscore variables?
body: <p>Related: <a href="https://stackoverflow.com/questions/1523427/python-what-is-the-common-header-format">What is the common header format of Python files?</a></p>
  <p><strong>Where can I find a list of all double-underscore variables that are commonly used in Python?</strong></p>
  <p>In Python, variables starting and ending with double underscores are typically to store metadata or are built into the system.  For example,</p>
  <pre><code>#!/usr/bin/env python
  
  __author__ = 'Michael0x2a'
  __license__ = 'GPL'
  
  class Test(object):
      def __init__(self):
          print 'Hello World!'
  
  if __name__ == '__main__':
      t = Test()
  </code></pre>
  <p>I'm pretty certain <code>__author__</code> and <code>__license__</code> are pretty well known.  What other double-underscore metadata variables are there?  Is there a comprehensive list I can check somewhere?  Can I just make up my own, or are there a bunch of ones that have become de-facto standards that I should use?</p>
  <p>Things like <code>__init__</code>, <code>__name__</code>, and <code>__doc__</code> are pretty much built into Python.  Are those the only reserved double-underscore variables?  Are there any more?  Is there some place I can get a list?</p>
  <p><strong>[Edit]</strong><br />
  I was browsing and encountered another <a href="https://stackoverflow.com/questions/1609716/i-need-closure">question</a> that linked to a <a href="http://www.mindmeister.com/10510492/python-underscore" rel="nofollow noreferrer">mindmap</a> of a bunch of double-underscore variables.</p>