Understanding "Callables" in Python

Python offers a concept known as a "callable," which encompasses anything that can be invoked like a function. The built-in callable function evaluates whether something possesses a __call__ method or a non-zero tp_call member.

The __call__ Method

The __call__ method is invoked when an object is treated like a function. It enables objects to behave like functions, allowing for custom functionality when invoked with parentheses.

Example

Consider the following example:

class Foo:
  def __call__(self):
    print('called')

foo_instance = Foo()
foo_instance()  # This invokes the __call__ method

In this case, calling foo_instance() triggers the __call__ method, resulting in "called" being printed to the console.