Arranging nested lists in python

Question

Consider the following list in python:

[[[1, 2], [3, 4], [5, 6], [7, 8]],
 [['a', 'b'], ['c', 'd'], ['e', 'f'], ['g', 'h']],
 [[21, 22], [23, 24], [25, 26], [27, 28]]]

The top level list contains 3 list values which in-turn consists of 4 individual lists. I need to arrange these this lists in the following order:

[[1, 2, 'a', 'b', 21, 22],
 [3, 4, 'c', 'd', 23, 24],
 [5, 6, 'e', 'f', 25, 26],
 [7, 8, 'g', 'h', 27, 28]]

I have tried to implement this requirement using itertools, for loops, list comprehension etc but was unable to get it. Could you provide me the necessary python code capable of doing this requirement?

Martijn Pieters · Accepted Answer · 2014-09-19 12:09:20Z

2

You need to use zip() here, then flatten out the resulting tuples with sublists:

[[i for sub in combo for i in sub] for combo in zip(*inputlist)]

Demo:

>>> inputlist = [[[1, 2], [3, 4], [5, 6], [7, 8]],
...  [['a', 'b'], ['c', 'd'], ['e', 'f'], ['g', 'h']],
...  [[21, 22], [23, 24], [25, 26], [27, 28]]]
>>> [[i for sub in combo for i in sub] for combo in zip(*inputlist)]
[[1, 2, 'a', 'b', 21, 22], [3, 4, 'c', 'd', 23, 24], [5, 6, 'e', 'f', 25, 26], [7, 8, 'g', 'h', 27, 28]]

answered Sep 19, 2014 at 12:09

Martijn Pieters

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Ashwini Chaudhary · Accepted Answer · 2014-09-19 12:12:05Z

1

Using itertools with map:

>>> from itertools import chain, izip, starmap
>>> map(list, starmap(chain, izip(*lst)))
[[1, 2, 'a', 'b', 21, 22],
 [3, 4, 'c', 'd', 23, 24],
 [5, 6, 'e', 'f', 25, 26],
 [7, 8, 'g', 'h', 27, 28]]

answered Sep 19, 2014 at 12:12

Ashwini Chaudhary

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