【脚本语言系列】关于Python面向对象，你需要知道的事

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():    passaeroplane = Aeroplane()

# -*- coding:utf-8 -*-class Aeroplane():    def __init__(self)        passaeroplane = Aeroplane()

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

Aeroplane's Name:  Allen Moore

继承

# -*- coding:utf-8 -*-class Aeroplane():    passclass Boeing7x7(Aeroplane):    passclass Airbus3x0(Aeroplane):    passget_a_boeing = Boeing7x7()get_an_airbus = Airbus3x0()

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

I'm a PlaneI'm a Plane

重载

重载方法

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

Plane Name: NormalBoeing Name: Plane 7X7 747Airbus Name: Plane 3X0 320

添加新成员

# -*- coding:utf-8 -*-# only for Python 3.xclass Aeroplane():    def __init__(self, name):        self.name = nameclass 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.xclass Aeroplane():    def __init__(self, name):        self.name = nameclass Boeing7x7(Aeroplane):    def __init__(self, name, price):        super(Boeing7x7,self).__init__()        self.price = priceget_a_boeing = Boeing7x7("747",100)print get_a_boeing.nameprint 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.xclass 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.nameprint 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 nameCommon Planeinside the getter, get the nameCommon Planeinside the setter, set the name

• decorator修饰符

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

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

10000

封装

保护私有特性

# -*- coding:utf-8 -*-# only for Python 3.xclass 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_namegive_me_an_aeroplane = Aeroplane("Common Plane")print give_me_an_aeroplane.namegive_me_an_aeroplane.name="HQ Plane"      print give_me_an_aeroplane.nameprint give_me_an_aeroplane._Aeroplane__name

inside the getter, get the nameCommon PlaneHQ PlaneCommon Plane

多态polymorphism

# -*- coding:utf-8 -*-# only for Python 3.xclass Aeroplane():    def __init__(self, name, size):        self.name = name        self.size = size    def who(self):        return self.name    def which(self):        return "xxx-"+self.sizeclass Airbus3x0(Aeroplane):    def which(self):               return "3x0-"+self.size    class Boeing7x7(Aeroplane):    def which(self):        return "7x7-"+self.sizeplane = 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 PlaneSize: xxx-0Name: AirbusSize: 3x0-340Name: BoeingSize: 7x7-747Name: Common PlaneSize: xxx-0Name: AirbusSize: 3x0-340Name: BoeingSize: 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 = colorclass Size():    def __init__(self, size):        self.size = sizeclass Aeroplane():    def __init__(self, color, size):        self.color = color        self.size = size    def about(self):        print "The Fruit is ", color.color, "and ", size.sizecolor = 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 namedtupleFruit = namedtuple("Fruit", "color size")fruit = Fruit('Yellow','Big')# fruit = Fruit(color="Yello",size="Big")print fruitprint fruit.colorprint fruit.sizeparts = {"color":"Yellow", "size":"Big"}fruit = Fruit(**parts)print fruitprint fruit.colorprint fruit.size# change key not allowed, change value allowedfruit1 = fruit._replace(color="Green", size="Big")print fruit1print fruit1.colorprint fruit1.size# add key-value partparts["status"]="Fresh"print partsfruit2 = Fruit(**parts)print fruit2print fruit2.colorprint fruit2.sizeprint fruit2.status

Fruit(color='Yellow', size='Big')YellowBigFruit(color='Yellow', size='Big')YellowBigFruit(color='Green', size='Big')GreenBig{'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.colorTypeError: __new__() got an unexpected keyword argument 'status'