How do I concatenate two lists while taking elements 1 by 1

Question

How do I concatenate two lists while taking elements 1 by 1 in Python?

Example:

listone = [1, 2, 3]
listtwo = [4, 5, 6]

Expected outcome:

>>> joinedlist
[1, 4, 2, 5, 3, 6]

score 4 · Answer 1 · answered Apr 15 '20 at 12:12

4

zip the lists and flatten with itertooos.chain:

from itertools import chain

list(chain.from_iterable(zip(listone, listtwo)))
[1, 4, 2, 5, 3, 6]

answered Apr 15 '20 at 12:12

yatu

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score 2 · Accepted Answer · answered Apr 15 '20 at 12:24

Using just list_comprehensions and no other fancy library you can do this:

In [825]: [j for i in zip(listone, listtwo) for j in i]                                                                                                                                                     
Out[825]: [1, 4, 2, 5, 3, 6]

score 1 · Answer 3 · answered Apr 15 '20 at 12:10

1

Here is a simple way:

x = []

for a in zip(listone,listtwo):
    x.extend(a)
x

Or if you want some black magic with chain from itertools:

list(chain(*zip(listone,listtwo)))

answered Apr 15 '20 at 12:10

Christian Sloper

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score 0 · Answer 4 · answered Apr 15 '20 at 12:27

0

Here is another way:

joinedlist = [x for pair in zip(listone, listtwo) for x in pair]

answered Apr 15 '20 at 12:27

Jim Eliot

21
3

1

I just realised that this is the same as @Mayank Porwal's great answer :-) – Jim Eliot Apr 15 '20 at 12:30

score 0 · Answer 5 · answered Apr 15 '20 at 12:35

U have many choice to get the output you expected.

Use nested looping

x = []
for a in zip(listone, listtwo):
    for b in a:
        x.append(b)

Single loop, just append and using index for a

x = []
for a in zip(listone, listtwo):
    x.append(a[0])
    x.append(a[1])

And single line looping(more simple)

x = [x for i in zip(listone, listtwo) for x in i]

If u print x for each point, the output will be: [1, 4, 2, 5, 3, 6]

How do I concatenate two lists while taking elements 1 by 1

5 Answers5