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In-Depth Python OOP

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Useful Functions

isinstance()

The isinstance() (is instance) is a Python built-in function that checks object is an instance of a certain class and return the bool value (True or False). This function takes 2 arguments: instance and class:

print(isinstance(662, int))
print(isinstance(25.3, int))

              
12

            
print(isinstance(662, int))
print(isinstance(25.3, int))
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You can use this function to check your instances:

class User:
pass

user = User()

print(isinstance(user, User))

              
123456

            
class User:
  pass

user = User()

print(isinstance(user, User))
copy

issubclass()

The issubclass() (is subclass) is a Python built-in function that checks class is a Child of another class:

class First:
pass

class Second(First):
pass

class Third(Second):
pass

print(issubclass(Second, First))
print(issubclass(Third, First))

              
1234567891011

            
class First:
    pass

class Second(First):
    pass

class Third(Second):
    pass

print(issubclass(Second, First))
print(issubclass(Third, First))
copy

The issubclass() function works with classes only. If you want to check the instance, use the type() function inside the issubclass():

class A:
pass

class B(A):
pass

instance = B()

print(issubclass(type(instance), A))

              
123456789

            
class A:
    pass

class B(A):
    pass

instance = B()

print(issubclass(type(instance), A))
copy

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Section 2. Chapter 6
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