Un-nesting nested lists

Question

Hi I was wondering how I could un-nest a nested nested list. I have:

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

I would like to to look as follows:

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

How to do it?

possible duplicate of [Making a flat list out of list of lists in Python](http://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python) — martineau, Oct 03 '13 at 22:27

score 12 · Accepted Answer · answered Oct 03 '13 at 22:12

12

>>> L = [[[1,2,3]], [[4,5,6]], [[7,8,9]]]
>>> [x[0] for x in L]
[[1, 2, 3], [4, 5, 6], [7, 8, 9]]

answered Oct 03 '13 at 22:12

Birei · Answer 2 · 2013-10-05T13:29:32.737

1

For multiple nestings:

def unnesting(l):
    _l = []
    for e in l:
        while isinstance(e[0], list):
            e = e[0]
        _l.append(e)
    return _l

A test:

In [24]: l = [[[1,2,3]], [[[[4,5,6]]]], [[[7,8,9]]]]
In [25]: unnesting(l)
Out[25]: [[1, 2, 3], [4, 5, 6], [7, 8, 9]]

edited Oct 05 '13 at 13:29

answered Oct 03 '13 at 22:22

Birei

score 0 · Answer 3 · answered Oct 07 '22 at 03:17

I found another solution that might be easier and quicker here and also mentioned here.

from itertools import chain

nested_list = [[[1,2,3]], [[4,5,6]], [[7,8,9]]]
my_unnested_list = list(chain(*nested_list))
print(my_unnested_list)

which results in your desired output as:

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

3 Answers3