python - 从列表中获取元素，循环方式

Question

我想从列表的列表中构造一个列表，循环方式。
所有第一个元素，然后所有第二个元素等等。
列表的大小不同。

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

应该转向:

[1, 4, 6, 7, 2, 5, 8, 3, 9, 10]。

Answer 1

您可以使用循环法 recipe来自 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]