Python __call__

__call__

Python 中有一个有趣的语法，只要定义类型的时候，实现__call__函数，这个类型就成为可调用的。换句话说，我们可以把这个类型的对象当做函数来使用，相当于重载了括号运算符。

#!/usr/bin/env python
# coding=utf-8

class g_dpm(object):

    def __init__(self,g):
        self.g=g

    def __call__(self,t):
        return (self.g*t**2)/2
e_dpm=g_dpm(9.8)
s=e_dpm(2)
print s

#!/usr/bin/env python
# coding=utf-8

class Animal(object):
    def __init__(self,name,legs):
        self.name=name
        self.legs=legs
        self.stomach=[]

    def __call__(self,food):
        self.stomach.append(food)
    def poop(self):
        if len(self.stomach)>0:
            return self.stomach.pop(0)
    def __str__(self):
        return 'A animal named %s' % (self.name)

cow=Animal('king',4) # we make a cow
dog=Animal('flopp',4) # we can make many animals
print 'We have 2 animals a cow name %s and dog named %s, both have %s legs' % (cow.name,dog.name,cow.legs)
print cow # here __str__ method work

# we give food to cow
cow('gras')
print cow.stomach
# we give food to dog
dog('bone')
dog('beef')
print dog.stomach

# What comes in most come out
print cow.poop()
print cow.stomach # empty stomach