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Python编程之属性和方法实例详解

Jun 10, 2016 pm 03:12 PM
python Attributes method

本文实例讲述了Python编程中属性和方法使用技巧。分享给大家供大家参考。具体分析如下:

一、属性

在python中,属性分为公有属性和私有属性,公有属性可以在类的外部调用,私有属性不能在类的外部调用。公有属性可以是任意变量,私有属性是以双下划线开头的变量。

下面我们定义一个People类,它有一个公有属性name,和一个私有属性__age。

class People():
def __init(self):
self.name='张珊'
self.__age=24

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我们创建一个People类的实例,P1,当我们调用它的私有属性__age时发现有如下错误。

>>> p1.__age
Traceback (most recent call last):
File "", line 1, in
p1.__age
AttributeError: 'People' object has no attribute '__age'

这就说明了私有属性不可以在类的外部使用。那么我们要想调用私有属性的值,就可以在类的内部通过定义一个方法来调用。

>>> class People():
def __init__(self):
  self.name='jack'
  self.__age=23
def showinfo(self):
  print(self.__age)
>>> p2=People()
>>> p2.showinfo()
23

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可能有人会问,为什么加上双下划线的属性,我们就不可以在类的外部调用了呢?那么下面我们就探讨下python面向对象的私有机制。

Python中以双下划线开头的属性和方法,在被实例化后会自动在其名字前加_classname.因为名字被改变了,所以自然无法通过双下滑线开头的名字来访问,从而达到不可进入的目的。

我们可以通过实例名.__dict__来查看对象的属性集合。

Python中不同于其他面向对象的编程语言,python的设计哲学就是简单至上,因此如果你真的想要调用私有属性的话还是可以调用的。

二、方法

在python中方法分为公有方法、私有方法、类方法和静态方法。

下面我们看一个比较完整的例子

#!/usr/bin/python
#coding:utf-8
__author__ = 'MXi4oyu'
class People():
  def __init__(self):
    self.name='张珊'
    self.__age=23
  def fun1(self):
    #共有方法可以在类的外部进行调用
    #可以通过对象名.方法名来调用
    print("共有方法")
  def __fun2(self):
    #私有方法不能在类的外部进行调用
    #可以在类的其他方法中调用私有方法
    print("私有方法")
  def funcshow(self):
    self.__fun2()
  @classmethod
  #类方法要加上@classmethod修饰器,类方法可以通过类名.方法名进行调用
  def fun3(self):
    print("类方法")
  @staticmethod
  #静态方法需要加上@staticmethod修饰器,静态方法不需要加self,
  #同样可以通过类名.方法名调用
  def fun4():
    print("静态方法")
if __name__=='__main__':
  p1=People()
  p1.fun1()
  p1.funcshow()
  People.fun3()
  People.fun4()
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希望本文所述对大家的Python程序设计有所帮助。

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