python – How to merge lists into a list of tuples?

The Question :

311 people think this question is useful

What is the Pythonic approach to achieve the following?

# Original lists:

list_a = [1, 2, 3, 4]
list_b = [5, 6, 7, 8]

# List of tuples from 'list_a' and 'list_b':

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

Each member of list_c is a tuple, whose first member is from list_a and the second is from list_b.

The Question Comments :

The Answer 1

475 people think this answer is useful

In Python 2:

>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> zip(list_a, list_b)
[(1, 5), (2, 6), (3, 7), (4, 8)]

In Python 3:

>>> list_a = [1, 2, 3, 4]
>>> list_b = [5, 6, 7, 8]
>>> list(zip(list_a, list_b))
[(1, 5), (2, 6), (3, 7), (4, 8)]

The Answer 2

143 people think this answer is useful

In python 3.0 zip returns a zip object. You can get a list out of it by calling list(zip(a, b)).

The Answer 3

13 people think this answer is useful

You can use map lambda

a = [2,3,4]
b = [5,6,7]
c = map(lambda x,y:(x,y),a,b)

This will also work if there lengths of original lists do not match

The Answer 4

8 people think this answer is useful

Youre looking for the builtin function zip.

The Answer 5

7 people think this answer is useful

I am not sure if this a pythonic way or not but this seems simple if both lists have the same number of elements :

list_a = [1, 2, 3, 4]

list_b = [5, 6, 7, 8]

list_c=[(list_a[i],list_b[i]) for i in range(0,len(list_a))]

The Answer 6

5 people think this answer is useful

I know this is an old question and was already answered, but for some reason, I still wanna post this alternative solution. I know it’s easy to just find out which built-in function does the “magic” you need, but it doesn’t hurt to know you can do it by yourself.

>>> list_1 = ['Ace', 'King']
>>> list_2 = ['Spades', 'Clubs', 'Diamonds']
>>> deck = []
>>> for i in range(max((len(list_1),len(list_2)))):
        while True:
            try:
                card = (list_1[i],list_2[i])
            except IndexError:
                if len(list_1)>len(list_2):
                    list_2.append('')
                    card = (list_1[i],list_2[i])
                elif len(list_1)<len(list_2):
                    list_1.append('')
                    card = (list_1[i], list_2[i])
                continue
            deck.append(card)
            break
>>>
>>> #and the result should be:
>>> print deck
>>> [('Ace', 'Spades'), ('King', 'Clubs'), ('', 'Diamonds')]

The Answer 7

5 people think this answer is useful

The output which you showed in problem statement is not the tuple but list

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

check for

type(list_c)

considering you want the result as tuple out of list_a and list_b, do

tuple(zip(list_a,list_b)) 

The Answer 8

1 people think this answer is useful

One alternative without using zip:

list_c = [(p1, p2) for idx1, p1 in enumerate(list_a) for idx2, p2 in enumerate(list_b) if idx1==idx2]

In case one wants to get not only tuples 1st with 1st, 2nd with 2nd… but all possible combinations of the 2 lists, that would be done with

list_d = [(p1, p2) for p1 in list_a for p2 in list_b]

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