python3 __call__ method

Brush face questions can see, this method did not understand what practical use, the official document as follows:

3.3.6. Emulating callable objects

object. __call__ (self[, args...])

　　 Called when the instance is “called” as a function; if this method is defined,  x(arg1, arg2, ...)  is a shorthand for  x.__call__(arg1, arg2, ...) .

The main achievement is the direct object class as a function call

E.g:

class Demo(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b

    def my_print(self,):
        print("a = ", self.a, "b = ", self.b)

    def __call__(self, *args, **kwargs):
        self.a = args[0]
        self.b = args[1]
        print("call: a = ", self.a, "b = ", self.b)

if __name__ == "__main__":
    demo = Demo(10, 20)
    demo.my_print()

    demo(50, 60)

The results are as follows:

a =  10 b =  20
call: a =  50 b =  60

 Note that: only when the class is defined def __call __ () method, we can achieve this function, otherwise a syntax error occurs, the document is to explain if this method is defined meaning.