python class

基本语法//属性与封装//方法//继承和组合//多态//特殊方法//wxpython

当时想用static变量想到类的..

基本语法

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class class_name(base_class):
    class_var
    def methods(self, args):
        do something

#!/usr/bin/python
# -*- coding: utf-8 -*-
class A:
    #classic class 没有父类
    """this is class A"""
    pass
    __slots__=('x','y')  # 可访问"槽"内外的属性
    def test(self):
        # classic class test
        """this is A.test()"""
        print "A class"
        
class B(object):
    #new class 有父类,python3 都是这种,引入了super的概念
    """this is class B"""
    __slots__=('x','y')  # 只能访问"槽"里面的属性
    pass
    def test(self):
        # new class test
        """this is B.test()"""
        print "B class"

        
if __name__ == '__main__':
    a=A()
    b=B()

python是动态语言..可以直接任意的添加属性(槽..封死去路)

构造函数__init__

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class Car(object):
    country = u'中国'
    def __init__(self, length, width, height, owner=None):
        self.owner = owner
        self.length = length
        self.width = width
        self.height = height
        self.country = "china"

属性

共有

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# 公有属性
del a.country
a.__class__.country

私有属性

  1. 加两个下划线 不能直接访问到

    _className__property

  2. 只加一个下划线 从自己约束不直接访问

  3. 前后都加两个下划线 系统自带属性

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#copyRight by heibanke

class Car(object):
    country = u'中国'
    def __init__(self, length, width, height, owner=None):
        self.__owner = owner
        
        assert length>0,"length must larger than 0"
        self._length = length
        self._width = width
        self._height = height

    def getOwner(self):
        return self.__owner
    def setOwner(self, value):
        self.__owner = value

    def getLength(self):
        return self._length
        
    def setLength(self,value):
        assert value>0,"length must larger than 0"
        self._length = value

@描述符

加上@property变成有getter的对象

然后就可以像用属性 使用 方法

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#copyRight by heibanke

class Car(object):
    country = u'中国'
    def __init__(self, length, width, height, owner=None):
        self._owner = owner
        self._length = length
        self._width = width
        self._height = height

    @property
    def owner(self):
        return self._owner
    @owner.setter
    def owner(self, value):
        self._owner = value
    @owner.deleter
    def owner(self):
        self._owner = None
    
    @property
    def length(self):
        return self._length
    @length.setter
    def length(self, value):
        assert value>0,"length must larger than 0"
        self._length = value

if __name__ == '__main__':
    a = Car(1.2,1.4,1.5,u'黑板客')
    print a.owner
    del a.owner
    print a.owner
    a.length=-1

..attr继续优化…

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#copyRight by heibanke

class Car(object):
    country = u'中国'
    __slots__=('length','width','height','owner','__dict__')
    
    def __init__(self, length, width, height, owner=None):
        self.owner = owner
        self.length = length
        self.width = width
        self.height = height
        
    def __getattr__(self,name): # 没找到的时候调用
        print "__getattr__",name
        return self.__dict__.get(name,None)
        
    def __setattr__(self,name,value):
        print "__setattr__",name
        if name!='owner':
            assert value>0, name+" must larger than 0"
        self.__dict__[name]=value
        
    def __delattr__(self,name):
        print "__delattr__",name
        if name=='owner':
            self.__dict__[name]=None

            
if __name__ == '__main__':
    a = Car(1.2,1.4,1.5,u'黑板客')
    """
    print a.owner
    del a.owner
    print a.owner
    a.length=1
    
    print a.country
    a.country = 'china'
    print a.country
    """
    a.name = u"一汽"

…attr与slots搭配使用时会产生的问题

没有 slots 没有对 dict 进行隐藏

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#!/usr/bin/env python
# -*- coding: utf-8 -*-
#copyRight by heibanke

class Car(object):
    country = u'中国'
    __slots__=('length','width','height','owner','__dict__')
    
    def __init__(self, length, width, height, owner=None):
        self.owner = owner
        self.length = length
        self.width = width
        self.height = height
        
    def __getattr__(self,name):
        print "__getattr__",name
        assert name in self.__slots__, "Not have this attribute "+name
        return self.__dict__.get(name,None)
        
    def __setattr__(self,name,value):
        print "__setattr__",name
        assert name in self.__slots__, "Not have this attribute "+name
        
        if name!='owner':
            assert value>0, name+" must larger than 0"
        self.__dict__[name]=value
        
    def __delattr__(self,name):
        print "__delattr__",name
        assert name in self.__slots__, "Not have this attribute "+name
        if name=='owner':
            self.__dict__[name]=None

if __name__ == '__main__':
    a = Car(1.2,1.4,1.5,u'黑板客')
    """
    print a.owner
    del a.owner
    print a.owner
    a.length=1
    
    print a.country
    a.country = 'china'    
    print a.country
    
    a.name = u"一汽"
    """

方法

类方法, 实例方法@classmethod, 静态方法@staticmethod, 特殊方法

  • 形式区别

通过类和实例进行,不能直接调用

有自己的特殊参数 self, cls

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> @classmethod
> def from_string(cls,date_as_string):
>     return cls(map(int,date_as_string.split('-')))
>
>

>

有自己的声明语法

  • 实质区别

绑定类

绑定实例对象

无绑定

特殊方法

属性访问

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__getattr__
__setattr__
__getattribute__

实例生成

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__init__
__new__

数字计算

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__add__ # 运算符重载
__sub__
__mul__
__div__
__pow__
__round__

调用方法

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__str__ # print
__repr__ # 在解释器中敲出这个类之后的显示(一般给计算机看的东西)
__len__
__bool__ # if

比较大小

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__cmp__
'''
l : less
t : than
e : equal
g : great
n : negative
'''
__lt__ __le__ __eq__ __ne__ __gt__ __ge__

集合访问

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__setslice__ __getsclice__ # 集合切片
__getitem__ __setitem__  # 字典遍历
__contains__ # if a in b

迭代器

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__iter__
__next__

继承

多重继承:

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class A:
    a = 1
    b = 1

class B(A):
    a = 2

class C(A):
    a = 3
    b = 3
    c = 3
    
class D(B,C):
    pass

import inspect
inspect.getmro(D) # Method Resolution Order 
# Classic Dfs
# New Bfs

钻石继承

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super(D,self).method()
多重继承之后只执行一遍...

组合

has a

is a

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class De(object):
    def __init__(self, *args):
        self.members = list(args)
       	
    def addMember(self, person):
        self.members.append(person)

本文标题:python class

文章作者:Renld

发布时间:2016年09月12日 - 21时06分

最后更新:2016年09月18日 - 19时44分

原始链接:http://renld.github.io/2016/09/12/class/

许可协议: "署名-非商用-相同方式共享 3.0" 转载请保留原文链接及作者。

文章目录
  1. 1. 基本语法
    1. 1.1. 构造函数__init__
  2. 2. 属性
    1. 2.0.1. 共有
    2. 2.0.2. 私有属性
    3. 2.0.3. @描述符
    4. 2.0.4. ..attr继续优化…
    5. 2.0.5. …attr与slots搭配使用时会产生的问题
  • 3. 方法
    1. 3.1. 特殊方法
      1. 3.1.1. 属性访问
      2. 3.1.2. 实例生成
      3. 3.1.3. 数字计算
      4. 3.1.4. 调用方法
      5. 3.1.5. 比较大小
      6. 3.1.6. 集合访问
      7. 3.1.7. 迭代器
  • 4. 继承
    1. 4.1. 多重继承:
    2. 4.2. 钻石继承
  • 5. 组合