I have a list with numbers:
numbers = [1, 2, 3, 4]
.
I would like to have a list where they repeat n
times like so (for n = 3
):
[1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4]
.
The problem is that I would like to only use itertools
for this, since I am very constrained in performance.
I tried to use this expression:
list(itertools.chain.from_iterable(itertools.repeat(numbers, 3)))
But it gives me this kind of result:
[1, 2, 3, 4, 1, 2, 3, 4, 1, 2, 3, 4]
which is obviously not what I need.
Is there a way to do this with itertools
only, without using sorting, loops and list comprehensions? The closest I could get is:
list(itertools.chain.from_iterable([itertools.repeat(i, 3) for i in numbers]))
,
but it also uses list comprehension, which I would like to avoid.
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Answer
Since you don’t want to use list comprehension, following is a pure (+zip
) itertools
method to do it –
from itertools import chain, repeat list(chain.from_iterable(zip(*repeat(numbers, 3)))) # [1, 1, 1, 2, 2, 2, 3, 3, 3, 4, 4, 4]