import time
def performance(unit):
    def fn(f):
        def printtime(*args,**kw):
            t1=time.time()
            r=f(*args,**kw)
            t2=time.time()
            t = (t2 - t1)*1000 if unit =='ms' else (t2 - t1)
            print 'call %s() in %f %s'%(f.__name__,t,unit)
            return r
        return printtime
 return fn
@performance('ms')
def factorial(n):
    return reduce(lambda x,y: x*y, range(1, n+1))

print factorial(10)