What is a “callable”?

Question

Now that it\'s clear what a metaclass is, there is an associated concept that I use all the time without knowing what it really means.

I suppose everybody made once

Answer 1

__call__ makes any object be callable as a function.

This example will output 8:

class Adder(object):
  def __init__(self, val):
    self.val = val

  def __call__(self, val):
    return self.val + val

func = Adder(5)
print func(3)