Python OOP(3) staticmethod和classmethod统计实例

staticmethod 统计实例

#!python2

#-*- coding:utf-8 -*-

class c1:

    amount_instance=0

    def __init__(self):

        c1.amount_instance+=1

    @staticmethod

    def printresult():

        print "Amount of Instance: " ,c1.amount_instance

class sub1(c1):

    #此处定义没有作用，因为只会引用c1中amount_instance

    amount_instance=0

    @staticmethod

    def printresult():

        print "call by sub1"

        c1.printresult()

class sub2(c1):

    #此处定义没有作用，因为只会引用c1中amount_instance

    amount_instance=0

i1,i2=c1(),c1()

i1.amount_instance

Amount of Instance:  2

c1.amount_instance

Amount of Instance:  2

s1,s2=sub1(),sub1()

s1.printresult()

call by sub1

Amount of Instance:  4

sub1.printresult()

call by sub1

Amount of Instance:  4

s3=sub2()

s3.printresult()

Amount of Instance:  5

classmethod 统计实例

#!python2

#-*- coding:utf-8 -*-

#利用类方法管理每个类的实例计数器

#父类使用一个类方法来管理状态信息,该信息根据树中的类不同而不同,而且储存在类上

#类方法调用的是当前类的amount_instance而不是父类中的amount_instance

class c1:

    amount_instance=0

    @classmethod

    def printresult(cls):

        cls.amount_instance+=1

    def __init__(self):

        self.printresult()

class sub1(c1):

    amount_instance=0

    def __init__(self):

        c1.__init__(self)

class sub2(c1):

    amount_instance=0

i1=c1()

i1.amount_instance

1

c1.amount_instance

1

s1,s2=sub1(),sub1()

s1.amount_instance

2

sub1.amount_instance

2

c1.amount_instance

1

s3,s4,s5=sub2(),sub2(),sub2()

s3.amount_instance

3

c1.amount_instance

1

所以

1)静态方法：适用于处理一个类的本地数据

2)类方法：适用于处理类层级中每个类的数据