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>>> from itertools import combinations
>>> L = [1, 2, 3, 4]
>>> [",".join(map(str, comb)) for comb in combinations(L, 3)]
['1,2,3', '1,2,4', '1,3,4', '2,3,4']
xxxxxxxxxx
from itertools import combinations
[",".join(map(str, comb)) for comb in combinations(L, 3)]