>>> import example
>>> example.fact(10)
3628800
>>>
>>> example.fact(0)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: Expected a positive value.
>>>
>>> example.fact(-1)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ValueError: Expected a positive value.
>>>