为什么我们在 python 的 for 循环中使用 range(len)? [英] Why we use range(len) in for loop in python?

问题描述

我已经开始学习python，现在正在学习python for loop.我正在使用在线资源来学习 python.但我对 for 循环有点困惑.

I have started learning python and now learning python for loop. I am using online source to learn python. But i am little but confused about for loop.

list = ["geeks", "for", "geeks"]
for index in range(len(list)):
    print (list[index])

和

list = ["geeks", "for", "geeks"]
for i in list:
    print(i)

一样那么为什么要使用 range(len) 方法呢?

are same then why to use range(len) method?

提前致谢.

推荐答案

对于这种简单的情况，for ind in range(len(sequence)) 通常被认为是一种反模式.但是，在某些情况下，使用索引很有用，例如当您需要重新分配给列表时:

For such simple case, for ind in range(len(sequence)) is generally considered an anti-pattern. The are cases when it's useful to have the index around, though, such as when you need to assign back to the list:

for ind in range(len(lst)):
    elem = lst[ind]
    # ... Do some processing
    lst[ind] = processed_elem

即使在这种情况下，range(len(...)) 用 enumerate:

Even in that case, range(len(...)) is better expressed with enumerate:

for ind, elem in enumerate(lst):
    # ... Do some processing
    lst[ind] = processed_elem

此外，正如在 comment，建议避免与内置变量名冲突的变量名，例如list.

Also, as already pointed out in a comment, it's recommended to avoid variable names that clash with built-ins, such as list.

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