python dict函数枚举对象 [英] python dict function on enumerate object

问题描述

如果我有一个枚举对象x，为什么要执行以下操作：

If I have an enumerate object x, why does doing the following:

dict(x)

清除枚举序列中的所有项目？

clear all the items in the enumerate sequence?

推荐答案

枚举创建一个迭代器。迭代器是一个只知道序列的当前项目以及如何获取下一个的python对象，但没有办法重新启动它。因此，一旦你在一个循环中使用了一个迭代器，它就不能给你任何更多的东西，似乎是空的。

enumerate creates an iterator. A iterator is a python object that only knows about the current item of a sequence and how to get the next, but there is no way to restart it. Therefore, once you have used a iterator in a loop, it cannot give you any more items and appears to be empty.

如果你想从一个迭代器可以调用列表。

If you want to create a real sequence from a iterator you can call list on it.

stuff = range(5,0,-1)
it = enumerate(stuff)
print dict(it), dict(it) # first consumes all items, so there are none left for the 2nd call

seq = list(enumerate(stuff)) # creates a list of all the items
print dict(seq), dict(seq) # you can use it as often as you want

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