Create a list of strings by joining elements of another list [duplicate]

Question

Possible Duplicate:
How do you split a list into evenly sized chunks in Python?
Merge two lists in python?

Original data in array:

a = ['1', '2', '3', '4', '5', '6', '7', '8', '9']

Desired output:

['1 2 3', '4 5 6', '7 8 9']

I know using the while statement is inefficient, so I need help in this.

What have you tried so far? Are you trying to merge groups of always three columns? — Pierre GM
– Pierre GM, Commented Sep 6, 2012 at 6:08
Your title doesn't seem to match the rest of the question. There's only one array, it seems, not three. Do you really want to turn the list of strings into lists of longer strings that join three adjacent elements, or do you really need something different? — Blckknght
– Blckknght, Commented Sep 6, 2012 at 6:13
@Blckknght: His username is Natsume - English is more than likely not his native tongue. Additionally, his question does not seem ambiguous to me. — voithos
– voithos, Commented Sep 6, 2012 at 6:17
The biggest inefficiency, in my opinion, would be to spend too much time trying to find the "best" way to do something. Time is often worth alot more than a few processor cycles. — Aesthete
– Aesthete, Commented Sep 6, 2012 at 6:30

spolto · Accepted Answer · 2012-09-06 06:44:07Z

19

[' '.join(a[i:i+3]) for i in range(0, len(a), 3)]

edited Sep 6, 2012 at 6:44

spolto

4,5614 gold badges29 silver badges34 bronze badges

answered Sep 6, 2012 at 6:10

Aesthete

18.9k6 gold badges38 silver badges46 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

Aesthete Over a year ago

Downvote? This produces the exact output requested by the OP.

spolto Over a year ago

Maybe it's because of the spurious leading [? (wasn't me btw)

Aesthete Over a year ago

Sneaky.. Bad copy/paste from the interpreter. Another reason copy/paste is bad for you! Thanks for finding the mistake.

Community · Accepted Answer · 2017-05-23 11:44:10Z

4

Reuse!

from itertools import islice

def split_every(n, iterable):
    i = iter(iterable)
    piece = list(islice(i, n))
    while piece:
        yield piece
        piece = list(islice(i, n))

a = ['1', '2', '3', '4', '5', '6', '7', '8', '9']
new_a = [' '.join(slice) for slice in split_every(3, a)]

Mainly using this.

edited May 23, 2017 at 11:44

CommunityBot

11 silver badge

answered Sep 6, 2012 at 6:11

voithos

70.9k12 gold badges107 silver badges120 bronze badges

1 Comment

voithos Over a year ago

This also produces the exact output. :/

Collectives™ on Stack Overflow

Create a list of strings by joining elements of another list [duplicate]

2 Answers 2

3 Comments

1 Comment

Linked

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Linked

Related