Python - 类(class)的变量 和 对象(object)的变量 详解 及 代码

类(class)的变量 和 对象(object)的变量 详解 及 代码

本文地址: http://blog.csdn.net/caroline_wendy/article/details/20356531

Python中, 类(class)的变量是所有对象共享使用, 只有一个拷贝, 所有对象修改, 都可以被其他对象所见;
对象(object)的变量由类的每个对象所拥有, 每个对象都包含自己的一份拷贝, 不会影响其他对象;
使用类的变量, ClassName.val; 而使用对象的变量,self.val;
类的方法, 是类使用的, 可以定义为静态(static)方法, 有两种方式:
#@staticmethod 或 method = staticmethod(method) ;

析构函数,  __del__(双下划线), 在程序结束会自动调用, 也可以手动调用, del obj, 即可.

代码如下:
# -*- coding: utf-8 -*-

#====================
#File: ClassExercise.py
#Author: Wendy
#Date: 2014-03-03
#====================

#eclipse pydev, python2.7

class GirlFriend:

population = 0

def __init__(self, name):
self.name = name
print('(Initialize {0})'.format(self.name))
GirlFriend.population += 1

def __del__(self): #析构器
print('{0} is being destroyed!'.format(self.name))
GirlFriend.population -= 1

if GirlFriend.population == 0:
print('{0} was the last one.'.format(self.name))
else:
#{0:d} 表示使用10进制输出
print('There are still {0:d} girl friends.'.format(GirlFriend.population))

def sayLove(self):
print('Greetings, my boy friend loves me, {0}.'.format(self.name))

#@staticmethod
def howMany():
print('We have {0:d} girl friends.'.format(GirlFriend.population))

howMany = staticmethod(howMany)

gf1 = GirlFriend('Caroline')
gf1.sayLove()
GirlFriend.howMany()

gf2 = GirlFriend('Wendy')
gf2.sayLove()
GirlFriend.howMany()

del gf1 #手动调用 程序结束会自动调用析构函数
del gf2

GirlFriend.howMany()

输出:
(Initialize Caroline)
Greetings, my boy friend loves me, Caroline.
We have 1 girl friends.
(Initialize Wendy)
Greetings, my boy friend loves me, Wendy.
We have 2 girl friends.
Caroline is being destroyed!
There are still 1 girl friends.
Wendy is being destroyed!
Wendy was the last one.
We have 0 girl friends.