statis.py 文件源码

def perm(n):
  """Permutations.
     n = number of elements

     Notation: P
                n

     All elements included: yes
     Can elements repeat:   no
     Order matters:         yes

     See: Number of ways there are to rearrange n elements.

     Practical example: amount of numbers with 3 distinct digits.
     Let the elements be: 1, 2, 3:

       123, 132, 213, 231, 312, 321
  """
  return factorial(n)