一个python类 的 示例

python类的定义是很方便的

class A(object):
    """docstsadfasdfring for A"""
    finger = 10  # class attribute defined here
    leg = 2
    age = 0
    def __init__(self, arg={}):
        super(A, self).__init__()
        self.arg = arg
        self.name = ''  # data attribute defined here
        self.age = 0    # data attribute和class attribute的区别就是函数的local变量
                        # 与函数外部变量的区别（把class看成函数）


    # special method 特殊方法以__开头和结束
    def __setitem__(self, key, item):  
        self.arg[key] = item

    def __getitem__(self, key):
        return self.arg[key]
        
    def __repr__(self):
        return str(self.name)
    
    # private method 私有方法只以__开头
    def __bb(self):
        print '__bb'  

    # public method
    def aa(self):  
        # 类属性应该是和实例无关的，不应该在这里修改，但可以改
        self.__class__.finger += 3  
        # 更不应该这样改类属性，很混乱
        # self.finger += 3  
        # 不应该有类似这样的写法,类属性先定义
        self.__class__.name = 'tom'
        # 类属性和实例属性同名
        self.age += 1
        self.__class__.age += 2
    
    # 类方法, 类属性应该在类方法中修改
    @classmethod
    def heteromorphosis(cls):
        cls.leg += 1
        # cls.finger == self.__class__.finger 
        # cls实在类方法中修改类属性，后者是在实例方法中修改类属性，有点不伦不类
        cls.finger += 1

a = A()
a.aa()
b = A()

print a.finger, b.finger, A.finger
print A.name, b.name
print a.age, A.age
A.heteromorphosis()
print a.leg, A.finger, a.finger

 

# encoding: UTF-8
class M(object):
    def __init__(self):
        # 这些值都存在实例的__dict__里
        self.hello = None
        self.foo = None
        self.ppp = None


m = M()

m.__dict__.update({'hello': 'world',  'foo': 'bar'})

print m.hello
print m.__dict__