使用python加入列表列表中的子列表

Question

I am a newbie to python and have been having an issue with list comprehension. Is there a way to extend subsists in a list of list like this

lst = [[0,0,0,0],[[x,x,x,x],[y,y,y,y]],[0,0,0,0],[0,0,0,0]]

I would like to end up with a following list, but I am not sure how to approach the problem:

lst = [[0,0,0,0],[x,x,x,x,y,y,y,y],[0,0,0,0],[0,0,0,0]]

I found this snippet of code but I am not sure how to make it operate on a second "level" of lists. I tried this:

print([x for y in lst for x in y])

Answer 1

Just go through each element and if it has a length of 2 (which means its a donut), add the two elements of that sublist together.

def flatten(data):
    new_data = [lists[0]+lists[1] if len(lists) == 2 else lists for lists in data]
    return new_data

data = [[1, 2, 3, 4], [[5, 6, 7, 8], [9, 10, 11, 12]], [13, 14, 15, 16]]
new_data = flatten(data)

Answer 2

For the example given, you can do as follows:

x,y=1,2
lst = [[0,0,0,0],[[x,x,x,x],[y,y,y,y]],[0,0,0,0],[0,0,0,0]]

map(lambda l: sum(l,[]) if isinstance(l[0],list) else l, lst)

#gives: [[0, 0, 0, 0], [1, 1, 1, 1, 2, 2, 2, 2], [0, 0, 0, 0], [0, 0, 0, 0]]

I assumed that x=1 , and y=2 .

Based on the image, it seems you have nested lists in the following way:

x,y=1,2
lst = [[[0,0,0,0]],[[[x,x,x,x],[y,y,y,y]]],[[0,0,0,0]],[[0,0,0,0]]]
# 0, x, and y in you case are lists/touples, but for this example there are ints.
# it should not matter anyway for this example.

map(lambda l: [sum(l[0],[])] if len(l[0])==2 else l, lst)
# relults in: [[[0, 0, 0, 0]], [[1, 1, 1, 1, 2, 2, 2, 2]], [[0, 0, 0, 0]], [[0, 0, 0, 0]]]