Core Python Programming (2nd Edition)

13.12. Built-in Functions for Classes, Instances, and Other Objects
13.12.1. issubclass()
The issubclass() Boolean function determines if one class is a subclass or descendant of another class.
It has the following syntax:
issubclass(sub, sup)
issubclass() returns TRue if the given subclass sub is indeed a subclass of the superclass sup (and False
otherwise). This function allows for an "improper" subclass, meaning that a class is viewed as a subclass
of itself, so the function returns true if sub is either the same class as sup or derived from sup. (A
"proper" subclass is strictly a derived subclass of a class.)
Beginning with Python 2.3, the second argument of issubclass() can be tuple of possible parent classes
for which it will return true if the first argument is a subclass of any of the candidate classes in the given
tuple.
13.12.2. isinstance()
The isinstance() Boolean function is useful for determining if an object is an instance of a given class. It
has the following syntax:
isinstance(obj1, obj2)
isinstance() returns TRue if obj1 is an instance of class obj2 or is an instance of a subclass of obj2 (and
False otherwise), as indicated in the following examples:
>>> class C1(object): pass
...
>>> class C2(object): pass
...
>>> c1 = C1()
>>> c2 = C2()
>>> isinstance(c1, C1)
True
>>> isinstance(c2, C1)
False
>>> isinstance(c1, C2)
False