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)