CODEWITHSUNDEEP
pythonlistmergetuples
rubayeet
rubayeet

Reputation: 9400

How to merge lists into a list of tuples?

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.

Upvotes: 368

Views: 378881

Answers (10)

Sadman Sakib
Sadman Sakib

Reputation: 605

Like me, if anyone needs to convert it to list of lists (2D lists) instead of list of tuples, then you could do the following:

list(map(list, list(zip(list_a, list_b))))

It should return a 2D List as follows:

[[1, 5], 
 [2, 6], 
 [3, 7], 
 [4, 8]]

Upvotes: 0

U13-Forward
U13-Forward

Reputation: 71610

Or map with unpacking:

>>> list(map(lambda *x: x, list_a, list_b))
[(1, 5), (2, 6), (3, 7), (4, 8)]
>>>

Upvotes: 2

YOU
YOU

Reputation: 123917

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)]

Upvotes: 558

Vipin
Vipin

Reputation: 99

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))]

Upvotes: 7

J0ANMM
J0ANMM

Reputation: 8551

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]

Upvotes: 1

cyborg
cyborg

Reputation: 878

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))

Upvotes: 6

Dark Knight
Dark Knight

Reputation: 879

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

Upvotes: 16

Kruger
Kruger

Reputation: 177

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')]

Upvotes: 5

Lodewijk
Lodewijk

Reputation: 3971

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

Upvotes: 147

Mizipzor
Mizipzor

Reputation: 52381

Youre looking for the builtin function zip.

Upvotes: 8

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