一、Class添加新方法: MethodType

1. 外挂类

   
   

class Animal(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def run(self):
        print 'Animal is run'

def set_color(self, color):
    self.color = color;
    print color

dog = Animal('Pity', 9)

cat = Animal('Miumiu', 9)

from types import MethodType
dog.set_color = MethodType(set_color, dog, Animal)

dog.set_color('yellow')

print dog.color

cat.set_color('white_yellow')

由此可见，MethodType指定添加在dog对象中，而非Animal中

2.内嵌类

class Animal(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def run(self):
        print 'Animal is run'

def set_color(self, color):
    self.color = color;
    print color

dog = Animal('Pity', 9)

cat = Animal('Miumiu', 9)

from types import MethodType
Animal.set_color = MethodType(set_color, None, Animal)

dog.set_color('yellow')

cat.set_color('white_yellow')

格式图：

二、Class限制添加新元素：__slots__

1. 普通的Class没有限制添加元素

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Animal(object):
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def run(self):
        print 'Animal is run'

dog = Animal('Pity', 9)

dog.color = 'yellow'  #dog实体添加了新元素color
print dog.color

2.限制添加新元素：__slots__

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Animal(object):
    __slots__ = ('name', 'age')  #限制实体添加其他元素
    def __init__ (self, name, age):
        self.name = name
        self.age = age
    def run(self):
        print 'Animal is run'

dog = Animal('Pity', 9)
print dog.name

dog.color = 'yellow'

！！！但是！！！！！

对于继承Animal的子类来讲，这个方法无效，除非在子类中也添加__slots__

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Animal(object):
    __slots__ = ('name', 'age')
    def __init__ (self, name, age):
        self.name = name
        self.age = age
    def run(self):
        print 'Animal is run'

class Cat(Animal):   #添加继承Animal的子类
    pass

cat = Cat('Miumiu', 9)
cat.color = 'white_yellow'
print cat.color