Whoever said Python wasn't dynamic?

>>> class X(object):

...   isX =  True

...

>>> class Y(object):

...   isY = True

...

>>> x =X()

>>> x.isX

True

>>> x.__class__



>>> x.__class__ = Y

>>> x.isX

Traceback (most recent call last):

  File "", line 1, in ?

AttributeError: 'Y' object has no attribute 'isX'

>>> x.isY

True

>>> x.bla = 'pir'

>>> x.bla

'pir'

>>> print x

<__main__.Y object at 0x007CACB0>

>>> x.__class__ = X

>>> x.isX

True

>>> x.bla

'pir'

>>>