Whether The Return Value Of A Function Modified By Python Decorator Can Only Be Nonetype

I wrote a decorator that gets the runtime of the program, but the function return value becomes Nonetype. def gettime(func): def wrapper(*args, **kw): t1 = time.time()

Solution 1:

Since the wrapper replaces the function decorated, it also needs to pass on the return value:

def wrapper(*args, **kw):
    t1 = time.time()
    ret = func(*args, **kw)  # save it here
    t2 = time.time()
    t = (t2-t1)*1000
    print("%s run time is: %.5f ms"%(func.__name__, t))
    return ret  # return it here

Solution 2:

Or you can do:

def gettime(func):
    def wrapper(*args, **kw):
        t1 = time.time()
        func(*args, **kw)
        t2 = time.time()
        t = (t2-t1)*1000
        print("%s run time is: %.5f ms"%(func.__name__, t))
        print("The correct rate is: %f"%func(*args,**kw))
    return wrapper


@gettime
def contrast(a, b):
    res = np.sum(np.equal(a, b))/a.size
    return res
contrast(A,B)