isinstance and issubclass (See related posts)

>>> class P(object):  # parent class
	pass

>>> class K(P):       # subclass
	pass

>>> k = K()           # instace
>>> isinstance(k, K)
True
>>> isinstance(k, P)
True
>>> isinstance(K, P)  # K is a class
False

>>> issubclass(K, P)
True
>>> issubclass(k, P)  # k is not a class

TypeError: issubclass() arg 1 must be a class

>>> isinstance(K, type)  # a class is an instace of type
True
>>> isinstance(k, type)  # not a class
False