Get the factorial of a number using python validations

factorial.py

#!/usr/bin/env python
# -*- coding: utf-8 -*-

factorial = 1

number = raw_input("Insert a number\n")

if number is '':
	print("No ingresaste Nada")
elif number.isspace():
	print("Insert some blank")
elif number.isalpha():
	print("Words don't have factorial")
elif int(number) < 0:
	print("Negative numbers don't have factorial")
elif int(number) is 0:
	print("Factorial of 0 is 1")
else:
	numberlimit = int(number) + 1
	long(factorial)

	for i in range(1, numberlimit):
		factorial = factorial * i
	print("The factorial of %s is %s")%(number,factorial)