def itersubclasses(cls, _seen=None):
"""
itersubclasses(cls)
Generator over all subclasses of a given class, in depth first order.
>>> list(itersubclasses(int)) == [bool]
True
>>> class A(object): pass
>>> class B(A): pass
>>> class C(A): pass
>>> class D(B,C): pass
>>> class E(D): pass
>>>
>>> for cls in itersubclasses(A):
... print(cls.__name__)
B
D
E
C
>>> # get ALL (new-style) classes currently defined
>>> [cls.__name__ for cls in itersubclasses(object)] #doctest: +ELLIPSIS
['type', ...'tuple', ...]
"""
if not isinstance(cls, type):
raise TypeError('itersubclasses must be called with '
'new-style classes, not %.100r' % cls)
if _seen is None: _seen = set()
try:
subs = cls.__subclasses__()
except TypeError: # fails only when cls is type
subs = cls.__subclasses__(cls)
for sub in subs:
if sub not in _seen:
_seen.add(sub)
yield sub
for sub in itersubclasses(sub, _seen):
yield sub
if __name__ == '__main__':
import doctest
doctest.testmod(verbose=1)
