Merge 2 lists in python

Question

Is there an elegant way to
[0,1,2,3], [4,5,6] - >[0,4,1,5,2,6,3]?

Answer 1

#Oneliner

a = [0,1,2,3,5,6]
b = [4,5,6]

print(sum([[i, j] for i, j in zip(a, b)] + [a[len(b):]] or [b[len(a):]], []))

Answer 2

This would be an inelegant way I suppose...

a, b = [0, 1, 2, 3, 4], [5, 6, 7]
c = []
for i in range(min((len(a), len(b)))):
c.append(a[i])
c.append(b[i])
c.extend(a[i+1:] or b[i+1])
print(c)

Answer 3

Yeah, the efficiency problem remains:

We create stuff we don't want.

Answer 4

I think this is most pythonic:
[x for x in chain.from_iterable(zip_longest(a, b)) if x is not None]

I also have another solution with pop() that consumes the original lists.

https://code.sololearn.com/ctGh1XLDz1nt/?ref=app

Answer 5

Hello are we on planet earth 👽
https://code.sololearn.com/cXiKi3ovUxTm/?ref=app
Oma Falk

Answer 6

There's itertools.zip_longest, which fills up the shorter iterables with None.

Answer 7

That will fill _ into the list, 𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥.

Sure, you can filter after that, but you're then losing elegance.

Answer 8

What mean is:

When you look at it, you should feel like damn, THAT'S how you do it, why didn't I think of that?

Answer 9

Not elegant but the most efficient and readable I could find.
https://code.sololearn.com/c501xOJcSnQY/?ref=app

[Edit] Oma Falk
#len(l2) >= len(l1)

res = [n for x in zip(l1,l2) for n in x] + l2[len(l1):]

I found the way to flatten a tuple here:
https://stackoverflow.com/questions/3204245/how-do-i-convert-a-tuple-of-tuples-to-a-one-dimensional-list-using-list-comprehe

Answer 10

But how do you get to the *end* result?

Answer 11

Yeah, as I said, list full of Nones.

Answer 12

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥, I mean, your version creates a list that has Nones in them, but then we make another list where we take the Nones out.

Answer 13

a = [0,1,2,3]
b = [4,5,6]

c = a + b
c[1:len(b)*2:2] = b
c[:len(b)*2+1:2] = a[:len(b)+1]

print(c)

# Put bigger list in "a" and smaller list in"b"

Answer 14

Speed comparison between different known methods mentioned in this thread:

https://code.sololearn.com/c39kIttuOIgd/?ref=app

Answer 15

Quick way,elegant way
Just Define a merge function
lst1 = [0,1,2,3]
lst2 = [4,5,6]
def mergeList(a,b):
return a + b
fulLst = mergeList(lst1,lst2)
print(fulLst)

Answer 16

not very elegant, but there's this...

print(sum(list(zip(a+b,b+a)), ())[0:len(a+b)])

Answer 17

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥 Sami Khan
my lists are not equal length 😒

Answer 18

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥
I remember a long zip in itertools🤔🤔
cant remember but that woukd make your zip variant perfect

Answer 19

𝐊𝐢𝐢𝐛𝐨 𝐆𝐡𝐚𝐲𝐚𝐥 not so bad!

Answer 20

This might be a bit late but....pip jnstall "more-itertools" then :-

import more_itertools

list1 = [1, 3, 5, 7]
list2 = [2, 4, 6, 8]
print(list(more_itertools.roundrobin(list1, list2)))

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