How to reformat variables in lists in list to make one list

Question

Very popular answer but my one differs from others. I have a list:

s = [(1, 2, 3),
     (4, 5, 6),
     (7, 8, 9)]

I need without another lists combine my lists inside and make one big list. I need them to be string so I do

[map(str, x) for x in s]

But in this way I get [['1', '2', '3'], ['4', '5', '6'], ['7', '8', '9']]

So I need ['1', '2', '3', '4', '5', '6', '7', '8', '9']

Possible duplicate of [Making a flat list out of list of lists in Python](https://stackoverflow.com/questions/952914/making-a-flat-list-out-of-list-of-lists-in-python) — ndmeiri, Feb 27 '18 at 08:13

score 2 · Accepted Answer · answered Feb 27 '18 at 08:12

2

You need list comprehension with flatenning:

print ([i for x in s for i in map(str, x)])
['1', '2', '3', '4', '5', '6', '7', '8', '9']

answered Feb 27 '18 at 08:12

jezrael

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Jay Shankar Gupta · Answer 2 · 2018-02-27T08:18:14.300

2

import itertools
s = [(1, 2, 3),
    (4, 5, 6),
    (7, 8, 9)]
print(list(map(str,itertools.chain(*s))))

edited Feb 27 '18 at 08:18

answered Feb 27 '18 at 08:16

Jay Shankar Gupta

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score 1 · Answer 3 · answered Feb 27 '18 at 08:14

1

You can use sum and list:

map(str, list(sum(s, ())))

answered Feb 27 '18 at 08:14

Maroun

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score 1 · Answer 4 · answered Feb 27 '18 at 08:14

1

Simply using a nestled list comprehension is perhaps the easiest

>>> [str(sii) for si in s for sii in si]
['1', '2', '3', '4', '5', '6', '7', '8', '9']

answered Feb 27 '18 at 08:14

Jonas Adler

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score 1 · Answer 5 · answered Feb 27 '18 at 08:51

1

Another option is to use reduce to make the flat list and map to cast elements to string.

>>> from functools import reduce

>>> s = [(1, 2, 3), (4, 5, 6),(7, 8, 9)]
>>> list(map(str,reduce(lambda x,y: x+y,s)))
>>> ['1', '2', '3', '4', '5', '6', '7', '8', '9']

answered Feb 27 '18 at 08:51

Sohaib Farooqi

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Tho concise, I find `reduce` a lot slower than most other more "verbose" ways in Python. Does anyone know why? – Calvin Ku Feb 27 '18 at 10:18
@CalvinKu [Here you go](https://stackoverflow.com/a/5436709/5741172) :) – Sohaib Farooqi Feb 27 '18 at 10:21

score 1 · Answer 6 · answered Feb 27 '18 at 14:43

1

itertools.chain is convenient for this purpose:

from itertools import chain

s = [(1, 2, 3),
     (4, 5, 6),
     (7, 8, 9)]

list(map(str, chain.from_iterable(s)))

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

answered Feb 27 '18 at 14:43

jpp

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How to reformat variables in lists in list to make one list

6 Answers6