从列表中获取元素，轮循样式 [英] Take elements from lists, round robin style

问题描述

我想以循环方式从列表列表构建列表.
所有第一个元素，然后所有第二个元素，等等.
列表的大小不一样.

I want to construct a list from a list of lists, round robin style.
All first elements, then all second elements etc.
The lists aren't the same size.

[[1, 2, 3], [4, 5], [6], [], [7, 8, 9, 10]]

应转到:

[1, 4, 6, 7, 2, 5, 8, 3, 9, 10].

推荐答案

您可以使用轮询食谱(来自itertools):

You can use the roundrobin recipe from itertools:

from itertools import cycle, islice

def roundrobin(*iterables):
    "roundrobin('ABC', 'D', 'EF') --> A D E B F C"
    # Recipe credited to George Sakkis
    num_active = len(iterables)
    nexts = cycle(iter(it).__next__ for it in iterables)  # .next on Python 2
    while num_active:
        try:
            for next in nexts:
                yield next()
        except StopIteration:
            # Remove the iterator we just exhausted from the cycle.
            num_active -= 1
            nexts = cycle(islice(nexts, num_active))

输出:

l = [[1,2,3],[4,5],[6],[],[7,8,9,10]]
print(list(roundrobin(*l)))
[1, 4, 6, 7, 2, 5, 8, 3, 9, 10]

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