python中try except语句块怎么用？

try:

    <>

except []:

    <>

while True:

    print('++++++两数相除的商：++++++')

    try:

        num1 = eval(input('被除数：'))

        num2 = eval(input('除数：'))

        result = num1/num2

        print('商 = 被除数/除数 =)

    except:

        print('!!!!!!程序出错重新开始!!!!!!')