一、Class添加新方法: MethodType

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__

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