CODEWITHSUNDEEP
pythonlist
user3014764
user3014764

Reputation: 9

How do I take a list of lists and rearrange them in python

I am trying to create a function that can do this.

>>> rearrange_list([1,2,3],[4,5,6])
[[1,4],[2,5],[3,6]]

So far what I have is

def rearrange_list(my_list):
    i = 0
    n = 0
    new_list = []
    for i in range(0, len(my_list[n])):
        for n in range(0,len(my_list)):
            new_list += [my_list[n][i]]
            print(new_list)
            n += 1
    return new_list

but this code returns [1, 4, 2, 5, 3, 6], a single list instead of a list of lists like I want it to and I can't seem to figure out how to make the function output a list of lists based on the index of the list inside the list.

Upvotes: 0

Views: 149

Answers (3)

user2555451
user2555451

Reputation:

You can use zip and a list comprehension:

>>> def rearrange_lists(a, b):
...     return [list(x) for x in zip(a, b)]
...
>>> rearrange_lists([1,2,3], [4,5,6])
[[1, 4], [2, 5], [3, 6]]
>>>

Note that the above function only handles two lists. If you want to handle any number of lists, you can use this:

>>> def rearrange_lists(*lsts):
...     return [list(x) for x in zip(*lsts)]
...
>>> rearrange_lists([1,2,3], [4,5,6], [7,8,9])
[[1, 4, 7], [2, 5, 8], [3, 6, 9]]
>>>

Upvotes: 1

agconti
agconti

Reputation: 18093

Use zip like so:

zip(list_a, list_b)

Upvotes: 1

Martijn Pieters
Martijn Pieters

Reputation: 1121524

Use zip() instead:

>>> zip([1,2,3], [4,5,6])
[(1, 4), (2, 5), (3, 6)]

or, for your specific varargs version:

>>> lsts = ([1,2,3], [4,5,6])
>>> zip(*lsts)
[(1, 4), (2, 5), (3, 6)]

or map the results to lists if tuples won't do:

map(list, zip([1,2,3], [4,5,6]))  # Python 2
[list(t) for t in zip([1,2,3], [4,5,6])]  # Python 2 and 3

As a replacement for your function:

def rearrange_list(*my_lists):
    return [list(t) for t in zip(*my_lists)]

Upvotes: 0

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