factorial()

Compute the factorial of a non-negative integer.

Usage

factorial(n)

Returns the product of all positive integers less than or equal to n. By convention, factorial(0) is 1.

Parameters

n: int

A non-negative integer whose factorial is to be computed.

Returns

int

The factorial of n.

Raises

ValueError

If n is negative.

Examples

>>> factorial(5)

120

>>> factorial(0)

1

Factorials grow very quickly:

>>> factorial(10)

3628800

>>> factorial(20)

2432902008176640000

Works with small values too:

>>> factorial(1)

1

>>> factorial(2)

2