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Python中的闭包的概念, 在我看来, 就相当于在某个函数中又定义了一个或多个函数, 内层函数定义了具体的实现方式, 而外层返回的就是这个实现方式, 但并没有执行, 除非外层函数调用的内层的实现方法被执行了。至于这个怎么执行, 看下面的例子就知道了

比如:

def sum_outer(x, y):
  def sum_in(z):
    return x + y - z;
  return sum_in #注意, 这里返回的不是sum_in() 只是sum_in的函数名

 m = sum_outer(3, 4) #3, 4 分别对应x, y,这里的m返回的也只是函数sum_in的定义,<function __main__.sum_in>
 print m(5) # m对应z, 这个时候才是真正sum_in执行的时候

看起来就像通过sum_outer 调用了内层的sum_in函数, 多了层代理

其中一种应用场景就是可以根据不同的参数,使用相同的实现去返回对应不同的结果,比如, 根据不同的配置获取不同的数据库连接, 或者要求在验证字符串长度时, 可以根据不同的最大长度验证(外层传递最大长度, 内层传递验证的字符串)。

在抽象化一点, 外层定义了一个环境, 内层则是在该环境中的要做的事情, 但这个事情还没做,
只是要做。当真正需要做的时候到这个环境中去做了就好了(外层的返回结果(m)执行内层的函数sum_in)
实际上, 直接给函数传递需要的所有参数, 直接返回结果, 如上面的sum_outer和sum_in, 直接通过

def sum(x,y,z):
  return x + y - z

不就结了吗,为社么还要闭包这个实现呢? 到目前来说, 只能看出他们是两种不同的实现方式, 更多的区别, 还有待日后的学习体验

以上所述就是本文的全部内容了,希望大家能够喜欢。

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