如何使用面向对象的方式进行设计

定义类/对象

# -*- coding:utf-8 -*- class Aeroplane(): pass aeroplane = Aeroplane() # -*- coding:utf-8 -*- class Aeroplane(): def __init__(self) pass aeroplane = Aeroplane() # -*- coding:utf-8 -*- class Aeroplane(): def __init__(self, name): self.name = name aeroplane = Aeroplane("Allen Moore") print "Aeroplane's Name: ", aeroplane.name Aeroplane's Name: Allen Moore

继承

# -*- coding:utf-8 -*- class Aeroplane(): pass class Boeing7x7(Aeroplane): pass class Airbus3x0(Aeroplane): pass get_a_boeing = Boeing7x7() get_an_airbus = Airbus3x0() # -*- coding:utf-8 -*- class Aeroplane(): def exclaim(self): print("I'm a Plane") class Boeing7x7(Aeroplane): pass class Airbus3x0(Aeroplane): pass get_a_boeing = Boeing7x7() get_an_airbus = Airbus3x0() get_a_boeing.exclaim() get_an_airbus.exclaim() I'm a Plane I'm a Plane

重载

重载方法

# -*- coding:utf-8 -*- class Aeroplane(): def __init__(self, name): self.name = name class Boeing7x7(Aeroplane): def __init__(self, name): self.name = "Plane 7X7 "+name class Airbus3x0(Aeroplane): def __init__(self, name): self.name = "Plane 3X0 "+name get_a_plane = Aeroplane("Normal") get_a_boeing = Boeing7x7("747") get_an_airbus = Airbus3x0("320") print "Plane Name: "+ get_a_plane.name print "Boeing Name: "+ get_a_boeing.name print "Airbus Name: "+ get_an_airbus.name Plane Name: Normal Boeing Name: Plane 7X7 747 Airbus Name: Plane 3X0 320

添加新成员

# -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, name): self.name = name class Boeing7x7(Aeroplane): def __init__(self, name): self.name = "Plane 7X7 "+name def get_a_pulse(self): print "Get a Pulse" get_a_boeing = Boeing7x7("747") print get_a_boeing.get_a_pulse()

调用旧成员

# -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, name): self.name = name class Boeing7x7(Aeroplane): def __init__(self, name, price): super(Boeing7x7,self).__init__() self.price = price get_a_boeing = Boeing7x7("747",100) print get_a_boeing.name print get_a_boeing.price --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-22-375953c61263> in <module>() 9 self.price = price 10 ---> 11 get_a_boeing = Boeing7x7("747",100) 12 print get_a_boeing.name 13 print get_a_boeing.price <ipython-input-22-375953c61263> in __init__(self, name, price) 6 class Boeing7x7(Aeroplane): 7 def __init__(self, name, price): ----> 8 super(Boeing7x7,self).__init__() 9 self.price = price 10 TypeError: super() argument 1 must be type, not classobj

操作属性

设置属性

property方法 # -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, input_name): self.hidden_name =input_name def get_name(self): print "inside the getter, get the name" return self.hidden_name def set_name(self,input_name): print "inside the setter, set the name" self.hidden_name = input_name name = property(get_name, set_name) give_me_an_aeroplane = Aeroplane("Common Plane") print give_me_an_aeroplane.name print give_me_an_aeroplane.get_name() give_me_an_aeroplane.name='Uncle Allen' give_me_an_aeroplane.set_name("Uncle Allen") inside the getter, get the name Common Plane inside the getter, get the name Common Plane inside the setter, set the name decorator修饰符 # -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, input_name): self.hidden_name =input_name @property def name(self): print "inside the getter, get the name" return self.hidden_name @name.setter def name(self,input_name): print "inside the setter, set the name" self.hidden_name = input_name give_me_an_aeroplane = Aeroplane("Common Plane") print give_me_an_aeroplane.name give_me_an_aeroplane.name='Uncle Allen' print give_me_an_aeroplane.name

优点： * 一处更改，处处更新 * 不设设置，不容设置

# -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, name, size): self.name = name self.size = size @property def used_oils(self): return 100*self.size give_me_an_aeroplane = Aeroplane("Common Plane", 100) print give_me_an_aeroplane.used_oils give_me_an_aeroplane.size=10 print give_me_an_aeroplane.used_oils # -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, name, size): self.name = name self.size = size @property def used_oils(self): return 100*self.size give_me_an_aeroplane = Aeroplane("Common Plane", 100) print give_me_an_aeroplane.used_oils give_me_an_aeroplane.size=10 10000

封装

保护私有特性

# -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, input_name): self.__name =input_name @property def name(self): print "inside the getter, get the name" return self.__name @name.setter def name(self,input_name): print "inside the setter, set the name" self.__name = input_name give_me_an_aeroplane = Aeroplane("Common Plane") print give_me_an_aeroplane.name give_me_an_aeroplane.name="HQ Plane" print give_me_an_aeroplane.name print give_me_an_aeroplane._Aeroplane__name inside the getter, get the name Common Plane HQ Plane Common Plane

多态polymorphism

# -*- coding:utf-8 -*- # only for Python 3.x class Aeroplane(): def __init__(self, name, size): self.name = name self.size = size def who(self): return self.name def which(self): return "xxx-"+self.size class Airbus3x0(Aeroplane): def which(self): return "3x0-"+self.size class Boeing7x7(Aeroplane): def which(self): return "7x7-"+self.size plane = Aeroplane("Common Plane","0") print "Name: "+plane.who() print "Size: "+plane.which() planeA = Airbus3x0("Airbus","340") print "Name: "+planeA.who() print "Size: "+planeA.which() planeB = Boeing7x7("Boeing","747") print "Name: "+planeB.who() print "Size: "+planeB.which() def call_plane(obj): print "Name: "+obj.who()+"\n"+"Size: "+obj.which() call_plane(plane) call_plane(planeA) call_plane(planeB) Name: Common Plane Size: xxx-0 Name: Airbus Size: 3x0-340 Name: Boeing Size: 7x7-747 Name: Common Plane Size: xxx-0 Name: Airbus Size: 3x0-340 Name: Boeing Size: 7x7-747

对象之间的关系

组合 composition

聚合 aggregation

# -*- coding:utf-8 -*- class Color(): def __init__(self, color): self.color = color class Size(): def __init__(self, size): self.size = size class Aeroplane(): def __init__(self, color, size): self.color = color self.size = size def about(self): print "The Fruit is ", color.color, "and ", size.size color = Color("Yellow") size = Size("Big") aeroplane = Aeroplane(color, size) aeroplane.about() The Fruit is Yellow and Big

其他

方法分类

实例方法(instance method)

类方法(class method)

# -*- coding:utf-8 -*- class Aeroplane(): count = 0 def __init__(self): Aeroplane.count += 1 def exclaim(self): print "This is an aeroplane." @classmethod def account(cls): print "They have ",cls.count," aeroplanes." aero_a = Aeroplane() aero_b = Aeroplane() aero_c = Aeroplane() print Aeroplane.account() They have 3 aeroplanes. 静态方法(static method) # -*- coding:utf-8 -*- class Aeroplane(): def __init__(self,name): self.name = name def exclaim(self): print "This is an aeroplane." @staticmethod def hello(): print "Welcome!" Aeroplane.hello() Welcome! --------------------------------------------------------------------------- NameError Traceback (most recent call last) <ipython-input-72-5eb75aa8c2ed> in <module>() 10 11 Aeroplane.hello() ---> 12 hello() NameError: name 'hello' is not defined

特殊方法(special method)/魔术方法(magic method)

# -*- coding:utf-8 -*- class BarCodes(): def __init__(self, code): self.code = code def equals(self, code): return self.code.lower() == code.code.lower() first = BarCodes("ha") second = BarCodes("Ha") first.equals(second) # -*- coding:utf-8 -*- class BarCodes(): def __init__(self, code): self.code = code def __eq__(self, code): return self.code.lower() == code.code.lower() first = BarCodes("ha") second = BarCodes("Ha") first == second True

命名元祖

# -*- coding:utf-8 -*- from collections import namedtuple Fruit = namedtuple("Fruit", "color size") fruit = Fruit('Yellow','Big') # fruit = Fruit(color="Yello",size="Big") print fruit print fruit.color print fruit.size parts = {"color":"Yellow", "size":"Big"} fruit = Fruit(**parts) print fruit print fruit.color print fruit.size # change key not allowed, change value allowed fruit1 = fruit._replace(color="Green", size="Big") print fruit1 print fruit1.color print fruit1.size # add key-value part parts["status"]="Fresh" print parts fruit2 = Fruit(**parts) print fruit2 print fruit2.color print fruit2.size print fruit2.status Fruit(color='Yellow', size='Big') Yellow Big Fruit(color='Yellow', size='Big') Yellow Big Fruit(color='Green', size='Big') Green Big {'color': 'Yellow', 'status': 'Fresh', 'size': 'Big'} --------------------------------------------------------------------------- TypeError Traceback (most recent call last) <ipython-input-31-5349e1cad48d> in <module>() 24 print parts 25 ---> 26 fruit2 = Fruit(**parts) 27 print fruit2 28 print fruit2.color TypeError: __new__() got an unexpected keyword argument 'status'