Call a class method from another Class in Python

# Call a class method from another class in Python

To call a class method from another class:

1. Instantiate the class in the other class.
2. Call the method on the instance of the class.
3. Pass all of the required arguments in the call to the method.

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class A:
    def method_a(self, a, b):
        return a + b


class B:
    def method_b(self, a, b):
        return A().method_a(a, b)


b1 = B()

print(b1.method_b(10, 15))  # 👉️ 25

We instantiated class A in class B in order to call method_a in method_b.

The classes don't take any arguments because they don't define an __init__() method.

The methods in the example are accessed on instances of the classes.

# Calling a static class method from another class

If you defined a static method, you don't have to instantiate the class to call the method from another class.

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class A:
    @staticmethod
    def method_a(a, b):
        return a + b


class B:
    def method_b(self, a, b):
        return A.method_a(a, b)


b1 = B()

print(b1.method_b(10, 15))  # 👉️ 25

We used the @staticmethod decorator to define a static method in the class.

Notice that we didn't have to create an instance of class A to be able to call method_a.

You can also call method_a and store the result in a class variable in the other class.

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class A:
    def method_a(self, a, b):
        return a + b


class B:
    result = A().method_a(15, 20)


print(B.result)

The result class variable is shared by all instances of class B.

# Instantiating classes that have an __init__ method

Here is an example of instantiating classes that also define an __init__() method.

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class A:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def method_a(self, a, b):
        return a + b


class B:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def method_b(self, a, b):
        return A(self.name, self.age).method_a(a, b)


b1 = B('bobby', 30)

print(b1.method_b(10, 15))

We had to pass the necessary arguments when instantiating class A in class B.

You can also pass an instance of class A as an argument when instantiating class B.

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class A:
    def method_a(self, a, b):
        return a + b


class B:
    def __init__(self, instanceA):
        self.instanceA = instanceA

    def method_b(self, a, b):
        return self.instanceA.method_a(a, b)


a1 = A()

b1 = B(a1)

print(b1.method_b(10, 15))  # 👉️ 25

Class B takes an instance of class A as an argument in its __init__() method.

Now we are able to access the instance in method_b to call method_a.

# Additional Resources

You can learn more about the related topics by checking out the following tutorials:

• Purpose of 'return self' from a class method in Python
• Convert a string to a Class object in Python
• Creating class instances from a Dictionary in Python
• How to Update or access Class variables in Python
• How to Create an incremental ID in a Class in Python
• How to get the File path of a Class in Python
• TypeError: Class() takes no arguments in Python [Solved]