python --闭包学习

闭包概念：

Closure:内部函数中对enclosing作用域的变量进行引用

enclosing作用域：函数内部与内嵌函之间

范例1：

#coding:utf-8

def set_passline(passline):
    def cmp(val):
        if val>= passline:
            print "passline is %d"%passline
            print "%d is pass"%val
        else:
            print "passline is %d"%passline
            print "%d is failed"%val
    return cmp

f_100=set_passline(60)
f_150=set_passline(90)

f_100(89)
f_150(89)

输出：

passline is 60
89 is pass
passline is 90
89 is failed

范例2：

#coding:utf-8
def my_sum(*arg):
    return sum(arg)
def my_average(*arg):
    return sum(arg)/len(arg)

def dec(func):
    def in_dec(*arg):
        print ('in_dec arg=',arg)
        if len(arg)==0:
            return 0
        for val in arg:
            if not isinstance(val,int):
                return 0
        return func(*arg)
    return in_dec

my_sum=dec(my_sum)
my_average=dec(my_average)
print my_sum(1,2,3,4,5)
print my_sum(1,2,3,4,5,'')
print my_average(1,2,3,4,5)
print my_average()

输出：

('in_dec arg=', (1, 2, 3, 4, 5))
15
('in_dec arg=', (1, 2, 3, 4, 5, '6'))
0
('in_dec arg=', (1, 2, 3, 4, 5))
3
('in_dec arg=', ())
0

闭包作用

1：封装

2：代码复用