Joint nested list in Python

Question

How to convert a nested list like below?

d = [[['a','b'], ['c']], [['d'], ['e', 'f']]]
-> [['a','b','c'], ['d','e','f']]

I found a similar question. But it's a little different. join list of lists in python [duplicate]

Update

Mine is not smart

new = []

for elm in d:
    tmp = []
    for e in elm:
         for ee in e:
              tmp.append(ee)
    new.append(tmp)

print(new)
[['a', 'b', 'c'], ['d', 'e', 'f']]

Possible duplicate of [Flatten (an irregular) list of lists](https://stackoverflow.com/questions/2158395/flatten-an-irregular-list-of-lists) — Mark Dickinson, Oct 09 '17 at 19:19

Woody Pride · Accepted Answer · 2017-10-09T19:25:06.837

2

Lots of ways to do this, but one way is with chain

from itertools import chain
[list(chain(*x)) for x in d]

results in:

[['a', 'b', 'c'], ['d', 'e', 'f']]

edited Oct 09 '17 at 19:25

answered Oct 09 '17 at 19:21

Woody Pride

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The `range(len(...)` indirection seems unnecessary. `[list(chain(*x)) for x in d]` would be enough. – Mark Dickinson Oct 09 '17 at 19:23
True, for some reason I gravitate to iterating over index rather than items, but changed answer as it is much easier. – Woody Pride Oct 09 '17 at 19:25

score 1 · Answer 2 · answered Oct 09 '17 at 20:16

1

sum(ls, []) to flatten a list has issues, but for short lists its just too concise to not mention

d = [[['a','b'], ['c']], [['d'], ['e', 'f']]]

[sum(ls, []) for ls in d]

Out[14]: [['a', 'b', 'c'], ['d', 'e', 'f']]

answered Oct 09 '17 at 20:16

f5r5e5d

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This is also nice! – jef Oct 09 '17 at 20:34

Chen A. · Answer 3 · 2017-10-09T19:28:18.327

0

This is a simple solution for your question

new_d = []
for inner in d:
    new_d.append([item for x in inner for item in x])

edited Oct 09 '17 at 19:28

answered Oct 09 '17 at 19:20

Chen A.

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Joint nested list in Python

Update

3 Answers3