import time, functools
def performance(unit):
   def perf_decorator(f):
       @functools.wraps(f)
       def wrapper(*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 wrapper
   return perf_decorator

@performance('ms')
def factorial(n):
   return reduce(lambda x,y: x*y, range(1, n+1))
print factorial.__name__