How do I check (at runtime) if one class is a subclass of another?

Question

You can use issubclass() like this assert issubclass(suit, Suit).

issubclass(class, classinfo)

Excerpt:

Return true if class is a subclass (direct, indirect or virtual) of classinfo.

You can use isinstance if you have an instance, or issubclass if you have a class. Normally thought its a bad idea. Normally in Python you work out if an object is capable of something by attempting to do that thing to it.

The issubclass(sub, sup) boolean function returns true if the given subclass sub is indeed a subclass of the superclass sup.

issubclass minimal runnable example

Here is a more complete example with some assertions:

#!/usr/bin/env python3

class Base:
    pass

class Derived(Base):
    pass

base = Base()
derived = Derived()

# Basic usage.
assert issubclass(Derived, Base)
assert not issubclass(Base, Derived)

# True for same object.
assert issubclass(Base, Base)

# Cannot use object of class.
try:
    issubclass(derived, Base)
except TypeError:
    pass
else:
    assert False

# Do this instead.
assert isinstance(derived, Base)

GitHub upstream.

Tested in Python 3.5.2.

You can use the builtin issubclass. But type checking is usually seen as unneccessary because you can use duck-typing.