The following error classes exist in Werkzeug:
All the exceptions implement this common interface:
Starting with Werkzeug 0.3 some of the builtin classes raise exceptions that look like regular python exceptions (eg
KeyError) but are
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 safely 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
KeyError but also a
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
If you want to use this functionality with custom exceptions you can create an instance of the aborter class:
As you can see from the list above not all status codes are available as errors. Especially redirects and other non 200 status codes that do not represent errors are missing. For redirects you can use the
redirect() function from the utilities.
If you want to add an error yourself you can subclass
from werkzeug.exceptions import HTTPException class PaymentRequired(HTTPException): code = 402 description = '
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
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
raise BadRequest(description='Request failed because X was not present')