Python中类的内置方法与继承关系实例-创新互联
1.类的内置方法
Python内部类：
所谓内部类，就是在类的内部定义的类，主要目的是为了更好的抽象现实世界。
例子：
汽车是一个类，汽车的底盘轮胎也可以抽象为类，将其定义到汽车内中，而形成内部类，
更好的描述汽车类，因为底盘轮胎是汽车的一部分。
内部类实例化方法：
方法1：直接使用外部类调用内部类
方法2：先对外部类进行实例化，然后再实例化内部类
out_name = outclass_name()
in_name = out_name.inclass_name()
in_name.method()
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
print("I am chinese")
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
jack = People.Chinese()
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
jack = People.Chinese() #外部类调用内部类
print jack.name #外部类调用内部类对象
另一种方法，外部类调用内部类对象
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
ren = People() #实例化外部类
jack = ren.Chinese() #实例化内部类
print jack.name #打印内部类属性
或
print People.Chinese.name
print People.Chinese().name魔术方法：
str(self)
构造函数与析构函数
构造函数:
用于初始化类的内部状态，Python提供的构造函数是__init__():
__init__():方法是可选的，如果不提供，python会给出一个默认的__init__方法。析构函数：
用于释放对象占用的资源，python提供的析构函数是__del__():
__del__():也是可选的，如果不提供，则python会在后台提供默认析构函数。构造函数str
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def __str__(self):
return "This is People class"
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
ren = People() #实例化外部类
print ren #默认执行__str__
__init__(self)初始化类：
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def __str__(self):
return "This is People class"
def __init__(self,c='white'): #类实例化时自动执行
self.color = c
self.think()
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
jack = People('green')
ren = People() #实例化外部类
print ren.color #通过对象访问属性是初始化后的值
print People.color #通过类访问还是原来的值
[root@localhost 20180110]# python test1.py
I am a black
I am a thinker
30
black
yellow
析构函数__del__()：释放资源
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def __str__(self):
return "This is People class"
def __init__(self,c='white'): #类实例化时自动执行
print ("initing...")
self.color = c
self.think()
f = open('test.py')
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
def __del__(self):
print ("del....")
self.f.close()
jack = People('green')
ren = People() #实例化外部类
print ren.color #通过对象访问属性是初始化后的值
print People.color #通过类访问还是原来的值垃圾回收机制：
Python采用垃圾回收机制来清理不再使用的对象;python提供gc模块释放不再使用的对象。
Python采用“引用计数”的算法方式来处理回收，即：当然某个对象在其作用域内不再被其
他对象引用的时候，python就自动化清除对象。
gc模块collect()可以一次性收集所有待处理的对象(gc.collect)
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
__age = 30 #私有属性
class Chinese(object):
name ="I am a Chinese."
def __str__(self):
return "This is People class"
def __init__(self,c='white'): #类实例化时自动执行
print ("initing...")
self.color = c
self.think()
f = open('test.py')
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
print self.__age
def __talk(self):
print "I am talking with Tom"
@classmethod #调用类的方法
def test(self):
print ("this is class method")
@staticmethod #调用类的方法
def test1():
print ("this is static method")
def __del__(self):
print ("del....")
self.f.close()
print gc.collect() 如果是0是没有回收的。
jack = People('green')
ren = People() #实例化外部类
print ren.color #通过对象访问属性是初始化后的值
print People.color #通过类访问还是原来的值2.类的继承
类的继承
继承是面向对象的重要特性之一，
继承关系继承是相对两个类而言的父子关系
子类继承了父类的所有公有属性和方法，
继承，实现了代码重用使用继承
继承可以重用已经存在的数据和行为，减少代码的重复编写,
Python在类名后使用一对括号来表示继承关系，括号中的即类为父类
class Myclass(ParentClass)，
如果父类定义了__init__方法，子类必须显式调用父类的__init__方法，
ParentClass.__init__(self,[args...])
如果子类需要扩展父类的行为，可以添加__init__方法的参数.
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def think(self):
self.color = "black"
print "I am a %s " % self.color
print ("I am a thinker")
class Chinese(People):
pass
cn = Chinese()
print cn.color
cn.think()
父类中有构造函数：
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def __init__(self):
print "Init..."
self.dwell = 'Earth'
def think(self):
print "I am a %s " % self.color
print ("I am a thinker")
class Chinese(People):
pass
cn = Chinese()
print cn.dwell
cn.think()
参数大于两个：
Super 函数
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def __init__(self,c):
print "Init..."
self.dwell = 'Earth'
def think(self):
print "I am a %s " % self.color
print ("I am a thinker")
class Chinese(People):
def __init__(self):
People.__init__(self,'red')
pass
cn = Chinese()
class A(object):
def __init__(self):
print "enter A"
print "leave A"
class B(object):
def __init__(self):
print "enter B"
super(B,self),__init__()
print "leave B"
b = B()
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def __init__(self,c):
print "Init..."
self.dwell = 'Earth'
def think(self):
print "I am a %s " % self.color
print ("I am a thinker")
class Chinese(People):
def __init__(self):
super(Chinese,self).__init__('red')
pass
cn = Chinese()
cn.think()
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def __init__(self,c):
print "Init..."
self.dwell = 'Earth'
def think(self):
print "I am a %s " % self.color
print ("I am a thinker")
class Chinese(People):
def __init__(self):
super(Chinese,self).__init__('red')
def talk(self):
print "I like taking."
cn = Chinese()
cn.think()
cn.talk()多重继承
Python支持多重继承，第一个类可以继承多个父类
语法:
class class_name(Parent_c1,Parent_c2,...)
注意:
当父类中出现多个自定义的__init__的方法时，
多重继承，只执行第一个累的__init_方法，其他不执行。#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
color = 'yellow'
def __init__(self):
print "Init..."
self.dwell = 'Earth'
def think(self):
print "I am a %s " % self.color
print ("My home is %s ") % self.dwell
class Martian(object):
color = 'red'
def __init__(self):
self.dwell = 'Martian'
class Chinese(People,Martian):
def __init__(self):
People.__init__(self)
cn = Chinese()
cn.think()
#!/usr/bin/env python
#-*- coding:utf-8 -*-
class People(object):
def __init__(self):
self.dwell = 'Earth'
self.color = 'yellow'
def think(self):
print "I am a %s " % self.color
print ("My home is %s ") % self.dwell
class Martian(object):
color = 'red'
def __init__(self):
self.dwell = 'Martian'
def talk(self):
print "I like talking"
class Chinese(Martian,People):
def __init__(self):
People.__init__(self)
cn = Chinese()
cn.think()
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