1. 要判断是否为空,否则 i[0]有问题
  2. 判断 i[1:]是否为数字(is.digit()), 否则也会报错
while True:
    try:
        pos=[0,0]
        s=input().split(";")
        alpha = ['A','S','W','D']
        for i in s:
            if i == '':
                continue
            alp = i[0]
            num = i[1:]
            if alp in alpha and len(i)<=3 and num.isdigit():
                if alp == 'A':
                    pos[0]-=int(num)
                elif alp == 'D':
                    pos[0] +=int(num)
                elif alp == 'W':
                    pos[1] += int(num)
                else:
                    pos[1] -= int(num)

        print(str(pos[0])+','+str(pos[1]))
    except:
        break