Python自定义类抛出WeekDayError异常未生效问题排查

你编写的代码中WeekDayError()仅完成了异常类的实例化操作，并未主动触发异常抛出流程。Python中必须使用raise关键字才能主动抛出异常，只有被raise触发的异常才会被外层的except语句捕获匹配。

将判断分支内的代码修改为如下内容即可：

if day not in Weeker.list:
    raise WeekDayError()

class WeekDayError(Exception):
    pass
    

class Weeker:
    list=["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]

    def __init__(self, day):
        if day not in Weeker.list:
            raise WeekDayError()

try:
    weekday = Weeker('Monday')
    print(weekday)
except WeekDayError:
    print("Sorry, I can't serve your request.")

内容的提问来源于stack exchange，提问作者Harald