On Sat, Dec 14, 2019 at 3:56 PM David Mertz <[email protected]> wrote:
> [...] compositions are simply the permutations on the full length of the
> list of each partition.
>
Using permutations of partitions would be overkill. For compositions of a
given fixed length, it's much easier to compute them directly using a
stars-and-bars approach. The OP is simply asking for all possible
placements of `m-1` "dividers" in the input string `s`, and those divider
positions can be computed directly using `itertools.combinations(range(1,
len(s)), m-1)`. That gives the following one-liner:
segment = lambda s, m: (tuple(s[i:j] for i, j in zip((0,)+c,
c+(len(s),))) for c in itertools.combinations(range(1, len(s)), m-1))
Example output is exactly as the OP requested:
>>> list(segment("12345", m=3))
[('1', '2', '345'), ('1', '23', '45'), ('1', '234', '5'), ('12', '3',
'45'), ('12', '34', '5'), ('123', '4', '5')]
--
Mark
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