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copied!<p><strong>Note:</strong> in the following I assume Python 3.x. For Python 2.x, use <a href="http://www.python.org/doc/newstyle/" rel="nofollow noreferrer">new style classes</a>, i.e. write <code>class T(object): pass</code> instead of <code>class T: pass</code>.</p> <ol> <li><p>First, define some classes:</p> <pre><code>>>> class T: pass ... >>> class S: pass ... >>> class U(T): pass ... </code></pre></li> <li><p>To get a list of classes defined in the current scope, iterate over the <a href="http://docs.python.org/3.1/library/functions.html#globals" rel="nofollow noreferrer"><code>globals</code></a> (or <a href="http://docs.python.org/3.1/library/functions.html#locals" rel="nofollow noreferrer"><code>locals</code></a>) and test whether they are an instance of <a href="http://docs.python.org/3.1/library/functions.html#type" rel="nofollow noreferrer"><code>type</code></a> (thus a class!) using <a href="http://docs.python.org/3.1/library/functions.html#isinstance" rel="nofollow noreferrer"><code>isinstance</code></a>:</p> <pre><code>>>> [n for n, o in globals().items() if isinstance(o, type)] ['S', 'U', 'T'] </code></pre></li> <li><p>Use <a href="http://docs.python.org/3.1/library/functions.html#issubclass" rel="nofollow noreferrer"><code>issubclass</code></a> to restrict your search to the subclasses of a given class (in this case <code>T</code>):</p> <pre><code>>>> [n for n, o in globals().items() if isinstance(o, type) and issubclass(o, (T,))] ['U', 'T'] </code></pre></li> <li><p>You may want to omit <code>T</code> itself:</p> <pre><code>>>> [n for n, o in globals().items() if o != T and isinstance(o, type) and issubclass(o, (T,))] ['U'] </code></pre></li> <li><p>To get all classes starting with a certain string, call <a href="http://docs.python.org/3.1/library/stdtypes.html#str.startswith" rel="nofollow noreferrer"><code>startswith</code></a> on the class name:</p> <pre><code>>>> [n for n, o in globals().items() if n.startswith('T') and isinstance(o, type)] ['T'] </code></pre></li> <li><p>To <em>flag</em> certain classes at creation, use a <a href="http://www.python.org/dev/peps/pep-3129/" rel="nofollow noreferrer">class decorator</a><sup>&dagger;</sup> to add an attribute, e.g. <code>__flagged__</code>:</p> <pre><code>>>> def flag(cls): ... cls.__flag__ = 'flagged' ... return cls ... >>> @flag ... class X: pass ... >>> @flag ... class Y: pass ... >>> class Z: pass ... </code></pre></li> <li><p>Now you can just select only those classed with the <code>__flag__</code> attribute:</p> <pre><code>>>> [n for n, o in globals().items() if isinstance(o, type) and hasattr(o, '__flag__')] ['X', 'Y'] </code></pre></li> </ol> <hr> <p>  <sup>&dagger;</sup>: As <a href="https://stackoverflow.com/users/18936/bobince">bobince</a> notes, class decorators are <a href="http://docs.python.org/dev/3.0/whatsnew/2.6.html#pep-3129-class-decorators" rel="nofollow noreferrer">new in Python 2.6</a>.</p>

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