问将列表部分展平到给定的级别

EN

def flatten(l, level=None):
    if level == 0:
        return l
    flattened = []
    for item in l:
        if isinstance(item, list):
            flattened.extend(flatten(item, level-1 if level is not None else None))
        else:
            flattened.append(item)

    return flattened

ls2 = [1,[2,3],[4,[5,6]]]

print(flatten(ls2, level=1))
# [1, 2, 3, 4, [5, 6]]

print(flatten(ls2, level=2))
# [1, 2, 3, 4, 5, 6]

print(flatten(ls2))
# [1, 2, 3, 4, 5, 6]

ls2 = [1,[2,3],[4,[5,6]]]

def make_list_of_list(a):
    return [[i]if not isinstance(i, list) else i for i in a]

def flatten(l):
    return [item for sublist in make_list_of_list(l) for item in sublist]

flatten(ls2) will result in [1, 2, 3, 4, [5, 6]]
flatten(flatten(ls2)) will result in [1, 2, 3, 4, 5, 6]