python基础教程学习笔记七

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对象的魔力

多态 polymorphism

Def (x,y):

Return x+y

Add(1,2)

       3

封装 encapsulation

继承 inheritance

类和类型

创建自已的类

>>>class Person:

#使用 self绑定方法

       def setName(self,name):

              self.name=name

       def getName(self):

              return self.name

       def greet(self):

              print('hello,world! I am %s .' % self.name)

>>>foo=Person()

>>>bar=Person()

>>>foo.setName('retacn yue')

>>>bar.setName('three yue')

>>>foo.name

'retacn yue'

>>>bar.name

'three yue'

>>>foo.getName()

'retacn yue'

>>>bar.getName()

'three yue’

>>>foo.greet()

hello,world! Iam retacn yue .

>>>bar.greet()

hello,world! Iam three yue .

特性函数和方法

>>>class Bird:

       song='qwuaawk!'

       def sing(self):

              print (self.song)

             

>>>bird=Bird()

>>>bird.sing()

qwuaawk!

>>>birdsong=bird.sing

>>>birdsong()

qwuaawk!

私有方法

>>>class Secretive:

       def __inaccessible(self):

              print('but you cant not seeme...')

       def accessible(self):

              print('the seccret message is:')

              self.__inaccessible()

             

>>>s=Secretive()

>>> 

>>>s.__inaccessible()

Traceback (mostrecent call last):

  File "<pyshell#142>", line 1,in <module>

    s.__inaccessible()

AttributeError:'Secretive' object has no attribute '__inaccessible'

>>>s.accessible()

the seccretmessage is:

but you cant notsee me...

注:实际上还参在类外访问这些方法

#3.0不能访问

 s._Secretive__inaccessible

<bound methodSecretive.__inaccessible of <__main__.Secretive object at 0x029B6B10>>

类的命名空间

>>>class MemberCounter:

       members=0

       def init(self):

              MemberCounter.members+=1

             

>>>m1=MemberCounter()

>>>m1.init()

>>>MemberCounter.members

1

>>>m2=MemberCounter()

>>> m2.init()

>>>MemberCounter.members

2

指定超类

>>> class Filter:

       definit(self):

              self.blocked=[]

       deffilter(self,sequence):

              return[x for x in sequence if x not in self.blocked]

      

>>> classSPAMFilter(Filter):#filter的子类

       definit(self):#重写filter超类中的init方法

              self.blocked=['SPAM']

             

>>> f=Filter()

>>> f.init()

>>> f.filter([1,2,3])

[1, 2, 3]

>>> s=SPAMFilter()

>>> s.init()

>>>s.filter(['SPAM','SPAM','SPAM','SPAM','egg','bacon','SPAM','SPAM'])

['egg', 'bacon']

检查继承

>>>issubclass(SPAMFilter,Filter)

True

>>>issubclass(Filter,SPAMFilter)

False

也可以使用特殊属性__bases__

>>>SPAMFilter.__bases__

(<class'__main__.Filter'>,)

>>>Filter.__bases__

(<class'object'>,)

多个超类

先继承类中的方法会重写后继承类中的方法

这一点与c++有点类似,多重继承

Java是单继承,接口可以实现多重继承

>>> classCalculator:

       def calculate(self,expression):

              self.value=eval(expression)

             

>>>class Talker:

       def talk(self):

              print('Hi! My value is ',self.value)

             

>>>class TalkingCalculator(Calculator,Talker):

       pass

>>>tc=TalkingCalculator()

>>> tc.calculate('1+2*3')

>>>tc.talk()

Hi! My value is7

接口和内省

#检查方法是否存在

>>>hasattr(tc,'talk')

True

>>>hasattr(tc,'test')

False

#检查方法是否可以调用

>>>callable(getattr(tc,'talk',None))

True

>>>callable(getattr(tc,'test',None))

False

#3.0中可以使用以下方法

>>>hasattr(getattr(tc,'test',None),'__call__')

False

>>>hasattr(getattr(tc,'talk',None),'__call__')

True