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Python函数中的函数(闭包)用法实例

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Release: 2016-06-10 15:05:51
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本文实例讲述了Python闭包的用法。分享给大家供大家参考,具体如下:

Python函数中也可以定义函数,也就是闭包。跟js中的闭包概念其实差不多,举个Python中闭包的例子。

def make_adder(addend):
  def adder(augend):
    return augend + addend
  return adder
p = make_adder(23)
q = make_adder(44)
print(p(100))
print(q(100))

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运行结果是:123和144.

为什么?Python中一切皆对象,执行p(100),其中p是make_adder(23)这个对象,也就是addend这个参数是23,你又传入了一个100,也就是augend参数是100,两者相加123并返回。

有没有发现make_adder这个函数,里面定义了一个闭包函数,但是make_adder返回的return却是里面的这个闭包函数名,这就是闭包函数的特征。

再看一个Python闭包的例子:

def hellocounter (name):
  count=[0]
  def counter():
    count[0]+=1
    print('Hello,',name,',',count[0],' access!')
  return counter
hello = hellocounter('ma6174')
hello()
hello()
hello()

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运行结果:

tantengdeMacBook-Pro:learn-python tanteng$ python3 closure.py 
Hello, ma6174 , 1 access!
Hello, ma6174 , 2 access!
Hello, ma6174 , 3 access!

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使用闭包实现了计数器的功能,这也是闭包的一个特点,返回的值保存在了内存中,所以可以实现计数功能。

转自:小谈博客 http://www.tantengvip.com/2015/07/python-closure/

希望本文所述对大家Python程序设计有所帮助。

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