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:

Nint, ndarray: Number of things.
kint, ndarray: Number of elements taken.
exactbool, optional: If True, calculate the answer exactly using long integer arithmetic (N and k must be scalar integers). If False, a floating point approximation is calculated (more rapidly) using poch. Default is False.

Returns:

valint, 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

>>> import numpy as np
>>> from scipy.special import perm
>>> k = np.array([3, 4])
>>> n = np.array([10, 10])
>>> perm(n, k)
array([  720.,  5040.])
>>> perm(10, 3, exact=True)
720