isinstance and issubclass

Learn type checks with isinstance and issubclass.

The isinstance function

isinstance(obj, Class) checks whether an object is an instance of a class (or its subclasses). It returns True or False.

Example: isinstance(d, Dog). If d is a Dog instance it returns True. If Dog inherits from Animal, then isinstance(d, Animal) also returns True. It accounts for the inheritance chain.

The issubclass function

issubclass(Child, Parent) checks whether a class is a subclass of another. It also returns True or False.

Example: issubclass(Dog, Animal). If Dog inherits from Animal it returns True. Here classes, not instances, are compared. isinstance is for instances; issubclass is for classes.

Exercise Try isinstance and issubclass

First define the Animal class (body pass). Then define class Dog(Animal): pass. Create an instance with d = Dog(). Write three lines: print(isinstance(d, Dog)), print(isinstance(d, Animal)) and print(issubclass(Dog, Animal)).

Show example solution

# Define the Animal and Dog classes
class Animal:
    pass

class Dog(Animal):
    pass

d = Dog()
print(isinstance(d, Dog))
print(isinstance(d, Animal))
print(issubclass(Dog, Animal))

Test yourself

What does isinstance(d, Dog) return?
- None
- False
- True
- Dog
Show answer

True — If d is a Dog instance, it returns True.
Match the functions

isinstance

Is instance?
issubclass

Is subclass?
type

Exact type

Complete the isinstance call

if isinstance(d, ____):
    print("Dog")

Show answer

if isinstance(d, Dog):
    print("Dog")

Next lesson: Summary - Inheritance

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