Python: Reconstruct a list by its element counts

user_4971866 0
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I had a list with several elements (0,1,2,3,...)

Now I have a dict with above unique elements as keys, their counts as values:

{0:1, 1:3, 2:4, 3:6}

And I want to reconstruct it back to a list

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

Is there any pythonic way the achieve this? vanilla or with numpy.

numpy python
3 Answers
from collections import Counter

c = Counter({0:1, 1:3, 2:4, 3:6})

list(c.elements())
user_14819860

You can simply use sum() for this:

d = {0:1, 1:3, 2:4, 3:6}
d = sum([[k]*v for k,v in d.items()], [])
user_141562270

This is a numpy way:

d = {0:1, 1:3, 2:4, 3:6}
np.repeat(list(d.keys()), list(d.values()))
user_30448250
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