SciPy

scipy.special.perm

scipy.special.perm(N, k, exact=False)[source]

Permutations of N things taken k at a time, i.e., k-permutations of N.

It’s also known as “partial permutations”.

Parameters :

N : int, ndarray

Number of things.

k : int, ndarray

Number of elements taken.

exact : bool, optional

If exact is False, then floating point precision is used, otherwise exact long integer is computed.

Returns :

val : int, ndarray

The number of k-permutations of N.

Notes

  • Array arguments accepted only for exact=False case.
  • If k > N, N < 0, or k < 0, then a 0 is returned.

Examples

>>> k = np.array([3, 4])
>>> n = np.array([10, 10])
>>> perm(n, k)
array([  720.,  5040.])
>>> perm(10, 3, exact=True)
720

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