范围(len(list))还是枚举(list)? [英] range(len(list)) or enumerate(list)?

问题描述

可能重复:
只需要索引:枚举或(x)范围?

哪些会被认为更好/更清晰/更快/更Pythonic"?我不关心列表L的内容，只关心它有多长.

Which of these would be considered better/clearer/faster/more 'Pythonic'? I don't care about the content of the list L, just how long it is.

a = [f(n) for n, _ in enumerate(L)]

或

a = [f(n) for n in range(len(L))]

如果有什么不同，f 函数也会使用 len(list).

If it makes any difference, the function f makes use of len(list) as well.

推荐答案

一些快速的计时运行似乎给使用 range() 的第二个选项比 enumerate():

Some quick timing runs seem to give the 2nd option using range() a slight edge over enumerate():

timeit a = [f(n) for n, _ in enumerate(mlist)]
10000 loops, best of 3: 118 us per loop

timeit a = [f(n) for n in range(len(mlist))]
10000 loops, best of 3: 102 us per loop

只是为了好玩，使用 xrange() (Python v2.7.2)

and just for fun using xrange() (Python v2.7.2)

timeit a = [f(n) for n in xrange(len(mlist))]
10000 loops, best of 3: 99 us per loop

我倾向于首先使用可读代码，然后使用 xrange()(如果可用)(即 Pre-Python v 3.x)，然后是 range() 和 enumerate().

I would favor readable code first, then using xrange() if available (i.e., Pre-Python v 3.x), followed by range() and enumerate().

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