def subclasses(cls, _found=()):
    """ Retourne toutes les classes héritant d'une classe """
 
    # On check que la classe est hérite bien de "object".
    # Utile uniquement pour un code 2.x qui utiliserait
    # des old style classes, qui n'ont pas "__subclasses__".
    if not isinstance(cls, type):
      raise TypeError('subclasses works only with new-style classes'
                            ', not %s' % cls)
 
    # On va stocker les classes rencontrées dans un set
    # pour éviter les doublons car on peut tomber sur
    # un héritage en forme de diamant.
    _found = _found or set()
 
    try:
      subs = cls.__subclasses__()
    except TypeError:  # Erreur levée si cls == type, petits vicieux
      subs = cls.__subclasses__(cls)
 
    for sub in subs:
        if sub not in _found:
            _found.add(sub)
            # Un appel récursif comme on les aimes
            subclasses(sub, _found)
 
    return _found

for x in subclasses(object):
    print x
## <type 'callable-iterator'>
## <class '_abcoll.Sized'>
## <type 'exceptions.EOFError'>
## <class '_abcoll.Mapping'>
## <type 'exceptions.UnicodeWarning'>
## <type 'exceptions.IOError'>
## <type 'memoryview'>
## <type 'code'>
## <type 'exceptions.ImportWarning'>
## <type 'sys.flags'>
## <type 'iterator'>
## <class 'warnings.catch_warnings'>
## <type 'exceptions.Warning'>
## <type 'exceptions.EnvironmentError'>
## <type 'dict'>
## <class 'encodings.utf_8.IncrementalEncoder'>
## <type 'weakproxy'>
## <class '_abcoll.Iterator'>
## <type 'sys.version_info'>
## <type 'posix.stat_result'>
## <type 'frozenset'>
## <class 'codecs.CodecInfo'>
## <class 'zipimport.ZipImportError'>
## <type 'exceptions.StopIteration'>
## <type 'exceptions.ImportError'>
## <class 'site._Printer'>
## <type 'weakref'>
## <class '_abcoll.Sequence'>
## <type 'property'>
## <class 'encodings.utf_8.IncrementalDecoder'>
## <type 'imp.NullImporter'>
## <type 'exceptions.TypeError'>
## <type 'bytearray'>
## <type 'int'>
## <type 'exceptions.UnicodeTranslateError'>
## <type 'instance'>
## <type 'exceptions.BaseException'>
## <type 'exceptions.SyntaxWarning'>
## <type 'file'>
## <class '_abcoll.MappingView'>
## <class '_weakrefset._IterationGuard'>
## <type 'exceptions.UnicodeDecodeError'>
## <type 'classobj'>
## <type 'exceptions.UnicodeError'>
## <class 'abc.abstractproperty'>
## <type 'exceptions.DeprecationWarning'>
## <type 'complex'>
## <type 'set'>
## <type 'buffer'>
## <type 'generator'>
## <type 'exceptions.Exception'>
## <class 'codecs.IncrementalDecoder'>
## <type 'exceptions.UserWarning'>
## <type 'staticmethod'>
## <type 'exceptions.UnicodeEncodeError'>
## <class 'encodings.CodecRegistryError'>
## <class '_abcoll.MutableSequence'>
## <class '_abcoll.KeysView'>
## <type 'cell'>
## <type 'exceptions.StandardError'>
## <type 'enumerate'>
## <type 'exceptions.KeyboardInterrupt'>
## <type 'exceptions.BufferError'>
## <class 'warnings.WarningMessage'>
## <type 'EncodingMap'>
## <class 'codecs.BufferedIncrementalDecoder'>
## <type 'exceptions.ValueError'>
## <class '_abcoll.Set'>
## <type 'exceptions.MemoryError'>
## <type 'exceptions.SystemExit'>
## <type 'reversed'>
## <class '_abcoll.Hashable'>
## <type 'bool'>
## <type 'classmethod'>
## <type 'exceptions.ReferenceError'>
## <type 'exceptions.GeneratorExit'>
## <class '_abcoll.Container'>
## <class '_abcoll.ItemsView'>
## <type 'xrange'>
## <type 'exceptions.PendingDeprecationWarning'>
## <type 'basestring'>
## <type 'exceptions.SystemError'>
## <type 'exceptions.ZeroDivisionError'>
## <class 'site.Quitter'>
## <type 'long'>
## <type 'NotImplementedType'>
## <type 'super'>
## <type 'fieldnameiterator'>
## <class '_abcoll.Callable'>
## <class '_abcoll.MutableSet'>
## <type 'exceptions.ArithmeticError'>
## <class 'abc.ABCMeta'>
## <type 'exceptions.OverflowError'>
## <type 'exceptions.FutureWarning'>
## <type 'sys.float_info'>
## <type 'formatteriterator'>
## <type 'type'>
## <type 'exceptions.AssertionError'>
## <type 'traceback'>
## <type 'exceptions.FloatingPointError'>
## <type 'function'>
## <type 'instancemethod'>
## <type 'sys.long_info'>
## <type 'builtin_function_or_method'>
## <class 'signal.ItimerError'>
## <class 'site._Helper'>
## <type 'exceptions.LookupError'>
## <type 'wrapper_descriptor'>
## <type 'exceptions.KeyError'>
## <class '_abcoll.ValuesView'>
## <type 'slice'>
## <class '_weakrefset.WeakSet'>
## <type 'list'>
## <type 'exceptions.IndexError'>
## <type 'getset_descriptor'>
## <type 'posix.statvfs_result'>
## <type 'exceptions.SyntaxError'>
## <type 'frame'>
## <class 'codecs.BufferedIncrementalEncoder'>
## <type 'PyCapsule'>
## <type 'exceptions.IndentationError'>
## <type 'NoneType'>
## <type 'zipimport.zipimporter'>
## <type 'member_descriptor'>
## <type 'exceptions.AttributeError'>
## <type 'ellipsis'>
## <type 'exceptions.UnboundLocalError'>
## <type 'unicode'>
## <class '_abcoll.Iterable'>
## <type 'exceptions.TabError'>
## <type 'exceptions.NameError'>
## <type 'tuple'>
## <class 'warnings._OptionError'>
## <type 'exceptions.NotImplementedError'>
## <type 'exceptions.RuntimeWarning'>
## <type 'str'>
## <class '_abcoll.MutableMapping'>
## <type 'exceptions.BytesWarning'>
## <type 'module'>
## <type 'exceptions.RuntimeError'>
## <class 'codecs.IncrementalEncoder'>
## <type 'float'>
## <type 'exceptions.OSError'>
## <type 'dictproxy'>
## <type 'weakcallableproxy'>