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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?

Answer 1

>>> 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]]

Answer 2

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]]

Answer 3

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]]