import time, functools

def performance(unit):

    def performance_decorator(f):

        @functools.wraps(f)

        def wrapper(*agrs,**kw):

            t1=time.time()

            r=f(*agrs,**kw)

            t2=time.time()

            t=(t2-t1)*1000 if unit=='ms' else (t2-t1)

            print 'call %s() %s %s' % (f.__name__,t,unit)

            return r

        return wrapper

    return performance_decorator

@performance('ms')

def factorial(n):

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

print factorial(2)

print factorial.__name__

为什么在第二行会输出 2 这个结果呢