import time

def performance(f):

    def fn(*args, **kw):

       t1 = time.time()

       r = f(*args,**kw)

       t2 = time.time()

       print 'call %s() in %fs' %(f._name_, (t2-t1))

       return r

    return fn

@performance

def factorial(n):

    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial(10)