Add clarification to zip's documentation

Documentation

Using zip on iterators of variable length results in a behavior that I believe would benefit from some additional clarification in the documentation. Take the following example:

>>> a = list(range(3))
>>> b = iter(range(100))
>>> list(zip(a, b))
[(0, 0), (1, 1), (2, 2)]
>>> list(zip(a, b))
[(0, 3), (1, 4), (2, 5)]

This is expected behavior as zip simply stops at the end of the shortest iterable, in this case a. When calling zip again a is restarted whilst b carries on from 3.

The unexpected behavior comes about when we swap the arguments putting the longer iterator as the first argument.

>>> a = list(range(3))
>>> b = iter(range(100))
>>> list(zip(b, a))
[(0, 0), (1, 1), (2, 2)]
>>> list(zip(b, a))
[(4, 0), (5, 1), (6, 2)]

Rather than carrying on from 3 like in the previous example we get a 4. I understand this is due to b being consumed during the zip and there is no way to know which iterator will yield a StopIteration first and so this is the intended behavior.

It may be beneficial to highlight this edge case in the documentation and make the recommendation to try and put the shortest iterator first.

从 Python 内置函数 zip 的文档开始，检查其中如何描述在最短的 iterable 处停止。明确说明迭代器可能会在达到 StopIteration 之前就被消耗，并记录所示的参数顺序边界情况，包括建议将最短的迭代器放在最前面。完成的标准是 zip 文档中清楚说明了该行为和建议。