Get permtutation count when using multiset_partitions

[Joan]

I am using the multiset_partitions from sympy to get the possible permutations of a list of elements, it does work wonderfully, but depending on the case it will take a long time to generate the whole list.

Is there any way I can calculate the number of permutations prior generating them? It would help to discard some complex calculations to be made.

Thanks

[Aaron Meurer]

The docstring of multiset_partitions describes how to count
partitions. It mentions the nT function, but not where to get it. It's
in sympy.functions.combinatorial.numbers

>>> from sympy.functions.combinatorial.numbers import nT
>>> from sympy.utilities.iterables import multiset_partitions
>>> len(list(multiset_partitions([1, 1, 2, 3], 3)))
4
>>> nT([1, 1, 2, 3], 3)
4

Also the docstring creates its own version of the Stirling numbers of
the second kind, but there is a striling() function in the same
module. So the documentation of multiset_partitions() could be
improved. Also, some of these functions should probably be included in
the default namespace (sympy/__init__.py).

Aaron Meurer

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[Joan]

Thanks Aaron,

I couldn't check on your suggestions until today, they worked great :D

Joan

Missatge de Aaron Meurer <asme...@gmail.com> del dia dl., 17 de juny 2019 a les 22:48:

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