isinstance operator returning false on inheritance

Question

I have created 2 classes A & B, B inherits A. I'm using the isinstance to check if b is of type a and it returns false. Shouldn't be true?

class a():pass

class b(a):pass

print isinstance(b,a)

Possible duplicate of [What is the difference between old style and new style classes in Python?](https://stackoverflow.com/questions/54867/what-is-the-difference-between-old-style-and-new-style-classes-in-python) — anthony sottile, Nov 23 '17 at 19:28

score 7 · Answer 1 · edited Sep 12 '13 at 19:53

7

No. b is an instance of either type or classobj, not of a. You may want the issubclass function instead.

>>> issubclass(b, a)
True

edited Sep 12 '13 at 19:53

Jeremy

answered Sep 12 '13 at 19:51

score 1 · Answer 2 · answered Sep 12 '13 at 19:53

1

b is class, not object, so it is not instance of any class. To get True, call isinstance(b(),a)

answered Sep 12 '13 at 19:53

Chocimier

It is actually an instance of one of two classes. But it is not an instance of `a`. – Ignacio Vazquez-Abrams Sep 12 '13 at 19:54

2 Answers2