·

13.39K

· calsaverini

If you want Flask to spit json objects when exceptions are raised inside the application code, this exception handler can be useful:

from flask import jsonify
from werkzeug.exceptions import default_exceptions
from werkzeug.exceptions import HTTPException


class JSONExceptionHandler(object):

 def __init__(self, app=None):
 if app:
 self.init_app(app)

 def std_handler(self, error):
 response = jsonify(message=error.message)
 response.status_code = error.code if isinstance(error, HTTPException) else 500
 return response


 def init_app(self, app):
 self.app = app
 self.register(HTTPException)
 for code, v in default_exceptions.iteritems():
 self.register(code)

 def register(self, exception_or_code, handler=None):
 self.app.errorhandler(exception_or_code)(handler or self.std_handler)

To test it, try running the following app:

from exception_handler import *
from werkzeug.exceptions import default_exceptions, NotFound
from flask import Flask

app = Flask(__name__)
handler = JSONExceptionHandler(app)

class UserNotFound(NotFound):
 def __init__(self, uid):
 super(UserNotFound, self).__init__()
 self.message = "Couldn't found a user with uid={}.".format(uid)


@app.route("/<int:uid>")
def home(uid):
 if uid != 0:
 raise UserNotFound(uid)
 else:
 return jsonify({'user': "Foo", "uid": 0})


if __name__ == "__main__":
 app.run(debug=True)

If you run this app, a GET request at http://localhost:5000/0 will return a JSON:

{"user": "Foo", "uid": 0}

and a GET request at http://localhost:5000/1 will return a JSON:

{"message": "Couldn't found a user with uid=1."}

You could also create custom exception handlers:

def zero_division_handler(error):
 return jsonify({"message": "Don't divide by zero!!!!!1111"})

handler.register(ZeroDivisionError, handler=zero_division_handler)

Related protips

Have a fresh tip? Share with Coderwall community!

Post

Post a tip

Sponsored by

#native_company#

#native_desc#

#native_cta#

Post a job for only 299ドル

Sponsored by #native_company# — Learn More