How to add method to a class using decorator in Python

Python – Add method to a class using decorator

To add method to a class in Python, you can use class decorator.

Here is an example of a class decorator.

def add_method(cls):
    def square(self, x):
        return x**2
    cls.square = square
    return cls

@add_method
class Calculator:
    pass

calc = Calculator()
print(calc.square(5))

Output

25

In the code

We defined a class decorator add_method that adds a new method square to the class it is applied to. The square method takes a single argument x and returns its square.

The add_method decorator takes a class as its argument, defines the square method, adds it to the class using the cls.square = square syntax, and returns the modified class.

We apply the decorator to the Calculator class using the @add_method syntax. When we create an instance of Calculator and call the square method on it, we get the expected output of 25, which is the square of 5.

References

• Python Decorators

Summary

In this tutorial, we learned how to define a decorator that adds a method to a class, with examples.