15

I have a nested list like this:

    my_list = [[1320120000000, 48596281], [1320206400000, 48596281], [1320292800000, 50447908]]

I would like to split it into something that looks like this:

    my_list1 = [48596281, 48596281, 50447908] 
    my_list2 = [1320120000000, 1320206400000, 1320292800000]

I know that this is fairly simple, but I haven't been able to get it to work. Any help would be much appreciated.

  • [from the python docs](http://docs.python.org/2/library/functions.html#zip). `zip() in conjunction with the * operator can be used to unzip a list` – kreativitea Oct 30 '12 at 23:56

3 Answers3

29

This is what the builtin function zip is for.

my_list2, my_list1 = zip(*my_list)

If you want lists instead of tuples, you can do 

my_list2, my_list1 = map(list, zip(*my_list))
istruble
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Antimony
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  • Thanks for your answer, and how can I do when I don't know how many nested lists are in `*my_list` ? – Revolucion for Monica Jul 05 '17 at 14:50
  • In such case probably `my_lists = zip(*my_list)` later on by len(my_lists) you will learn how many lists you get in the end. – Drachenfels Sep 11 '17 at 12:53
  • what I found disturbing with `zip` is that even your nested list are perfectly symmetrical you may end up with messy data, for that reason list comprehension is probably slightly better, please consider: `ab = [['a', 'A', 0], ['b', 1], ['c', 'C', 2]]; print(list(zip(*ab))); [('a', 'b', 'c'), ('A', 1, 'C')]` – Drachenfels Sep 11 '17 at 12:57
8

You can use list comprehension.

my_list1 = [i[1] for i in my_list]
my_list2 = [i[0] for i in my_list]
Tim
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4

using list comprehension:

In [6]: lis1,lis2=[x[0] for x in my_list],[x[1] for x in my_list]
In [7]: lis1
Out[7]: [1320120000000L, 1320206400000L, 1320292800000L]

In [8]: lis2
Out[8]: [48596281, 48596281, 50447908]

or using operator.itemgetter():

In [19]: lis1,lis2=map(itemgetter(0),my_list) , map(itemgetter(1),my_list)

In [20]: lis1
Out[20]: [1320120000000L, 1320206400000L, 1320292800000L]

In [21]: lis2
Out[21]: [48596281, 48596281, 50447908]

timeit comparisons:

In [42]: %timeit lis1,lis2=[x[0] for x in my_list],[x[1] for x in my_list]  #winner if lists are required
100000 loops, best of 3: 1.72 us per loop

In [43]: %timeit my_list2, my_list1 = zip(*my_list) # winner if you want tuples
1000000 loops, best of 3: 1.62 us per loop

In [44]: %timeit my_list2, my_list1 = map(list, zip(*my_list))
100000 loops, best of 3: 4.58 us per loop

In [45]: %timeit lis1,lis2=map(itemgetter(0),my_list),map(itemgetter(1),my_list)
100000 loops, best of 3: 4.4 us per loop
Ashwini Chaudhary
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  • if each tuple has three elements [(a,b,c) (x,y,z)] and I want to extract (a,b) (x,y) in one place and (c,z) in another place. how to proceed please tell. – DJ_Stuffy_K Mar 15 '18 at 19:16