Factorial.py

def factorial(x):
    result = 1
    for i in xrange(1, x + 1):
        result *= i
    return result

######################################################################

def _if(test):
    return lambda alternative: \
               lambda result: \
                   [delay(result), delay(alternative)][not not test]()
def delay(f):
    if callable(f): return f
    else: return lambda: f
fact = lambda n: _if (n <= 1) (1) (lambda: n * fact(n-1))
fact(100)