自定义异常

import os

class ExistsError(Exception):   # 自定义异常，将要定义的异常继承Exception，就可以在捕捉异常那里捕捉到
    pass

class KeyInvalidError(Exception):
    pass


def new_func(path,prev):
    """
    去path路径的文件中，找到前缀为prev的一行数据，获取数据并返回给调用者
        1000，成功
        1001，文件不存在
        1002，关键字为空
        1003，位置错误
    :param path:
    :param prev:
    :return:
    """
    response = {‘code‘:1000,‘date‘:None}
    try:
        if not os.path.exists(path):
            raise ExistsError()
        if not prev:
            raise KeyInvalidError()
    except ExistsError as e:
        response[‘code‘]=1001
        response[‘date‘]= "文件不存在"
    except KeyInvalidError as e:
        response[‘code‘] = 1002
        response[‘date‘] = "关键字为空"
    except Exception as e:
        response[‘code‘] = 1003
        response[‘date‘] = "未知错误"
    return response

class MyExceptError(Exception):
    def __init__(self,key,value):
        self.key = key
        self.value = value

try:
    raise MyExceptError(‘1001‘,"关键字为空")
except MyExceptError as e:
    print(e)