What is __call__ in Python?

Python exposes a lot of built-in methods which can help us override almost any operation with the objects. One of those methods is __call__ method.

If we define a __call__ method then, it allows us to use the instance as a function.

class Demo:
    def __init__(self):
    	print('instantiated a class')

    def __call__(self):
    	print('instance is called')
        
a = Demo()
# instantiated a class


a()
# instance is called

In the above example, we can call the instance of Demo class and then use it as a function call.

What are the advantages of using __call__ ?

• A lot of libraries use __call__ method for implementing a clear interface for APIs
• Using __call__ also, help you get the best of both worlds where you are using OOP advantage while using simple function call syntax.
• There is a great StackOverflow answer mentioned below which highlights most of the use cases.