9. About Responses¶
The return value from a view function is automatically converted into a
response object for you. If the return value is a string it’s converted
into a response object with the string as response body, a
status code and a text/html mimetype. The logic that Flask applies to
converting return values into response objects is as follows:
- If a response object of the correct type is returned it’s directly returned from the view.
- If it’s a string, a response object is created with that data and the default parameters.
- If a tuple is returned the items in the tuple can provide extra
information. Such tuples have to be in the form
(response, status, headers)or
(response, headers)where at least one item has to be in the tuple. The
statusvalue will override the status code and
headerscan be a list or dictionary of additional header values.
- If none of that works, Flask will assume the return value is a valid WSGI application and convert that into a response object.
If you want to get hold of the resulting response object inside the view
you can use the
Imagine you have a view like this:
@app.errorhandler(404) def not_found(error): return render_template('error.html'), 404
You just need to wrap the return expression with
make_response() and get the response object to modify it, then
@app.errorhandler(404) def not_found(error): resp = make_response(render_template('error.html'), 404) resp.headers['X-Something'] = 'A value' return resp