.. automodule:: werkzeug.exceptions
The following error classes exist in Werkzeug:
.. autoexception:: BadRequest
.. autoexception:: Unauthorized
.. autoexception:: Forbidden
.. autoexception:: NotFound
.. autoexception:: MethodNotAllowed
.. autoexception:: NotAcceptable
.. autoexception:: RequestTimeout
.. autoexception:: Conflict
.. autoexception:: Gone
.. autoexception:: LengthRequired
.. autoexception:: PreconditionFailed
.. autoexception:: RequestEntityTooLarge
.. autoexception:: RequestURITooLarge
.. autoexception:: UnsupportedMediaType
.. autoexception:: RequestedRangeNotSatisfiable
.. autoexception:: ExpectationFailed
.. autoexception:: ImATeapot
.. autoexception:: PreconditionRequired
.. autoexception:: TooManyRequests
.. autoexception:: RequestHeaderFieldsTooLarge
.. autoexception:: InternalServerError
.. autoexception:: NotImplemented
.. autoexception:: BadGateway
.. autoexception:: ServiceUnavailable
.. exception:: HTTPUnicodeError This exception is used to signal unicode decode errors of request data. For more information see the :ref:`unicode` chapter.
.. autoexception:: ClientDisconnected
All the exceptions implement this common interface:
.. autoexception:: HTTPException :members: get_response, __call__
Starting with Werkzeug 0.3 some of the builtin classes raise exceptions that
look like regular python exceptions (eg :exc:`KeyError`) but are
:exc:`BadRequest` HTTP exceptions at the same time. This decision was made
to simplify a common pattern where you want to abort if the client tampered
with the submitted form data in a way that the application can't recover
properly and should abort with 400 BAD REQUEST.
Assuming the application catches all HTTP exceptions and reacts to them properly a view function could do the following savely and doesn't have to check if the keys exist:
def new_post(request):
post = Post(title=request.form['title'], body=request.form['body'])
post.save()
return redirect(post.url)
If title or body are missing in the form a special key error will be raised which behaves like a :exc:`KeyError` but also a :exc:`BadRequest` exception.
Sometimes it's convenient to just raise an exception by the error code, without importing the exception and looking up the name etc. For this purpose there is the :func:`abort` function.
.. function:: abort(status)
It can be passed a WSGI application or a status code. If a status code
is given it's looked up in the list of exceptions from above and will
raise that exception, if passed a WSGI application it will wrap it in
a proxy WSGI exception and raise that::
abort(404)
abort(Response('Hello World'))
If you want to use this functionality with custom exceptions you can create an instance of the aborter class:
.. autoclass:: Aborter
As you can see from the list above not all status codes are available as errors. Especially redirects and ather non 200 status codes that represent do not represent errors are missing. For redirects you can use the :func:`redirect` function from the utilities.
If you want to add an error yourself you can subclass :exc:`HTTPException`:
from werkzeug.exceptions import HTTPException
class PaymentRequired(HTTPException):
code = 402
description = '<p>Payment required.</p>'
This is the minimal code you need for your own exception. If you want to add more logic to the errors you can override the :meth:`~HTTPException.get_description`, :meth:`~HTTPException.get_body`, :meth:`~HTTPException.get_headers` and :meth:`~HTTPException.get_response` methods. In any case you should have a look at the sourcecode of the exceptions module.
You can override the default description in the constructor with the description parameter (it's the first argument for all exceptions except of the :exc:`MethodNotAllowed` which accepts a list of allowed methods as first argument):
raise BadRequest('Request failed because X was not present')