SciPy

scipy.misc.factorial

scipy.misc.factorial(n, exact=False)[source]

The factorial function, n! = special.gamma(n+1).

If exact is 0, then floating point precision is used, otherwise exact long integer is computed.

  • Array argument accepted only for exact=False case.
  • If n<0, the return value is 0.
Parameters :

n : int or array_like of ints

Calculate n!. Arrays are only supported with exact set to False. If n < 0, the return value is 0.

exact : bool, optional

The result can be approximated rapidly using the gamma-formula above. If exact is set to True, calculate the answer exactly using integer arithmetic. Default is False.

Returns :

nf : float or int

Factorial of n, as an integer or a float depending on exact.

Examples

>>> arr = np.array([3,4,5])
>>> sc.factorial(arr, exact=False)
array([   6.,   24.,  120.])
>>> sc.factorial(5, exact=True)
120L

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