###### tags: `Flask`
# Python Flask API 例外處理

* 概念：
* 在API的function前方加上@exception_handler裝飾器，功能邏輯需要return錯誤的時候，就直接raise自定義的exception。
* 所有例外要回傳的訊息統一用exception_hadler管理。
* 另外可以在自定義例外類別，客製化例外訊息、http status、error code。

## API

from utils.exception_handler import exception_handler

@app.route('/user', methods=['POST'])
@exception_handler
def user_create():
    api_key = request.headers.get('api-key')
    if api_key != customer_api_key:
        raise ApiHeaderAuthError()
        # raise ApiHeaderAuthError(message="other info", info="other info", code="error-001", status=501)

    data = request.json
    identity = data['identity']
    friendly_name = data['friendly_name']

    client.conversations.services(service_id).users.create(identity=identity, friendly_name=friendly_name, attributes=data)
    return jsonify({"message": "user created successfully"})

## utils.exception_handler

import sys
import traceback
from functools import wraps

from flask import jsonify
from twilio.base.exceptions import TwilioRestException
from utils.exceptions import *

"""
    抓取父類的例外，可以連同繼承此父類的例外都擷取到。
"""


def exception_handler(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        try:
            return func(*args, **kwargs)
        except TwilioRestException as e:
            return jsonify({"info": str(e.msg)}), e.status

        except ApiError as e:
            # print(e.__class__.__name__)  # 可以查看例外子類class名稱
            return {"code": e.code, "message": e.message, "info": e.info}, e.status

        except KeyError as e:
            return {"message": "key error", "info": str(e)}, 400

        except Exception as e:
            traceback.print_tb(sys.exc_info()[2])

            return {"message": "Something wrong", "info": str(e)}, 500
    return wrapper

## utils.exceptions

class ApiError(Exception):
    """ A generic 400 or 500 level exception from the Twilio API

    :param str|None message: A human-readable brief message for the error
    :param str|None info: Detail information about the error
    :param str|None code: A self-defined error code for the error
    :param int|500 status: the HTTP status that was returned for the exception

    """

    def __init__(self, message=None, info=None, code=None, status=500):
        self.message = message
        self.info = info
        self.code = code
        self.status = status

    def __str__(self):
        return self.message


class ApiHeaderAuthError(ApiError):
    def __init__(self, message="Header auth failed.", info=None, code=None, status=401):
        super().__init__(message, info, code, status)

###### tag: `Flask` `exception`