Question

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Python code to pick out all possible combinations from a list?

I have a list say [1, 2, 3]. I want to find the all the combinations

C(3,1)
[1] [2] [3]

C(3,2)
[1,2] [2,3] [1,3]

C(3,3)
[1,2,3]

Is there some module/library for doing this?

Answer 1

You can use itertools.combinations

>>> import itertools

>>> list(itertools.combinations([1,2,3], 1))
[(1,), (2,), (3,)]

>>> list(itertools.combinations([1,2,3], 2))
[(1, 2), (1, 3), (2, 3)]

>>> list(itertools.combinations([1,2,3], 3))
[(1, 2, 3)]

or generally for your C:

def C(a, b):
    return list(itertools.combinations(range(1,a+1), b))