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I'd like to transform a list ["A", "B", "C"] to a new list ["A", "A", "B", "B", "C", "C"]. I can think of an ugly loopy way of doing it but is there a one liner?

pitosalas
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3 Answers3

2

I would use itertools.repeat

import itertools
n= 2
print([repetition for i in range(10)
           for repetition in itertools.repeat(i,n) ])

OUTPUT

[0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9]
Bernardo stearns reisen
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  • If you're doing two loops already, you don't need `itertools.repeat`, just use `[i for i in original_input for _ in range(n)]` – Blckknght Apr 03 '20 at 01:36
1
  • You can use itertools.chain with zip to achieve desired result.
from itertools import chain
l = [1,2,3]
list(chain.from_iterable(zip(l,l)))

Output:

[1,1,2,2,3,3]
Poojan
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0

How about list concatenation with itertools?

import itertools
a = ["A", "B", "C"]
c = list(itertools.chain(*[ 2*x for x in a] ))
print(c)

OUTPUT

['A', 'A', 'B', 'B', 'C', 'C']

You could always replace the 2 with a variable.

001001
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