创建迭代器以逐个返回每个iterable中的元素

你可以用 itertools.chain.from_iterable() None 价值观:

from itertools import chain, zip_longest

it = (v for v in chain.from_iterable(zip_longest(l1, l2)) if v is not None)

而不是使用 作为sentinel值,您可能需要使用专用的sentinel,以便可以使用 没有一个 在输入列表中:

_sentinel = object()
flattened = chain.from_iterable(zip_longest(l1, l2, fillvalue=_sentinel))
it = (v for v in flattened if v is not _sentinel)

falsey values filter(None, ...)

it = filter(None, chain.from_iterable(zip_longest(l1, l2)))

演示:

>>> from itertools import chain, zip_longest
>>> l1 = [1, 2, 3, 4, 5, 6]
>>> l2 = ['a', 'b', 'c', 'd']
>>> it = (v for v in chain.from_iterable(zip_longest(l1, l2)) if v is not None)
>>> list(it)
[1, 'a', 2, 'b', 3, 'c', 4, 'd', 5, 6]

>>> l1 = [1, None, 2, None, 3, None]
>>> l2 = ['a', 'b', 'c', 'd']
>>> _sentinel = object()
>>> flattened = chain.from_iterable(zip_longest(l1, l2, fillvalue=_sentinel))
>>> it = (v for v in flattened if v is not _sentinel)
>>> list(it)
[1, 'a', None, 'b', 2, 'c', None, 'd', 3, None]

itertools recipes section 还有:

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)
    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))

l

import itertools
l1=[1,2,3,4,5,6]
l2=['a','b','c','d']

def flat_zip(l1,l2):
    for x,y in itertools.zip_longest(l1,l2):
        if x:
            yield x
        if y:
            yield y
it=flat_zip(l1,l2)

尽管我建议使用上面的内置解决方案。

仅使用列表理解。 评论中的解释。 仅为变更添加。

A = [1, 2, 3, 4, 5, 6]
B = ["A", "B", "C"]

# zipping equal length 
flattened_zip_list = [item for sublist in zip(A, B) for item in sublist]

print(flattened_zip_list )

# leftover from longest list 
extra_list = [A[index] for index in range(min(len(A), len(B)), max(len(A), len(B)) if len(A) > len(B) else B[index])]

print(extra_list)

# final list 
flattened_zip_list.extend(extra_list)

print(flattened_zip_list)

输出

[1, 'A', 2, 'B', 3, 'C'] # after zipping same lengths 
[4, 5, 6] # leftover values 
[1, 'A', 2, 'B', 3, 'C', 4, 5, 6] # [1, 'a', 2, 'b', 3, 'c', 4, 'd', 5, 6], the one mentioned in question 

[Program finished]