__call__

__call__ 函数，将类实例当做函数使用，弱化了函数和对象的区别。

class Person(object):
    def __init__(self, name, gender):
        self.name = name
        self.gender = gender

    def __call__(self, friend):
        print('I am %s' % self.name)
        print('My friend is %s' % friend)

p = Person('Bob', 'male')
p('Tim')