Evolution of a Python programmer(gist.github.com)

  import urllib
  import json

  def fact(n):
     res = urllib.urlopen('http://math.org/factorial/?' +
         urllib.urlencode({'n':n, 'format':'json'})).read()
     return json.loads(res)['answer']
  fact(6)

  # "close enough" programmer
  import math
  def fact(x):
    math.sqrt(2*math.pi*n) * math.pow(n/math.e, n)
  print fact(6)

  # lazy-er programmer
  def fact(x):
    factorials = {6:720} # found on my calculator, add more as they come up
    if factorials.has_key(x):
      return factorials[x]
    else:
      raise NotImplementedError
  print fact(6)

    def factorial(x):
        return x * factorial(x-1) if x > 1 else 1

    import operator
    def factorial(n):
        return reduce(operator.mul, xrange(1, n+1), 1)
    print factorial(6)

   import math
   print(math.factorial(6))

  class FactorialCommand(object):
      def set_num(self, num):
          self.__num = num

      def get_num(self):
          return self.__num

      def execute(self):
          result = 1
          i = 2
          while i <= self.get_num():
              result = result * i
              i = i + 1
          return result

  cmd = FactorialCommand()
  cmd.set_num(6)
  print cmd.execute()

  def fact(n):
      return eval('*'.join([str(x+1) for x in xrange(n)] + ['1']))

  def fact(l):
      return sum(map(bool,reduce(lambda I,l:''.join([l for I in I]),
                                 ['+'+'+'*l for l in xrange(l)])))
  assert fact(6)==720

  (*$:@:<:)^:(1&<) 6

    from math import factorial

    >>> reduce(int.__mul__, range(1,6))
    120

    fact = init_fact()
    ...
    res = fact[x]