Question

Given a simple Flask application, I’m just curious about whether there is a proper way to modify a Response in the hooks such as process_response?

e.g. Given:

from flask import Flask, Response

class MyFlask(Flask):
    def process_response(self, response):
        # edit response data, eg. add "... MORE!", but
        # keep eg mimetype, status_code
        response.data += "... This is added" # but should I modify `data`?
        return response
        # or should I:
        #     return Response(response.data + "... this is also added",
        #                     mimetype=response.mimetype, etc)

app = MyFlask(__name__)

@app.route('/')
def root():
    return "abddef"

if __name__ == '__main__':
    app.run()

Is it proper to just create a new response each time, or is it canonical to just edit in-place the response parameter and return that modified response?

This may be purely stylistic, but I’m curious – and I haven’t noticed anything in my reading that would indicate the preferred way to do this (even though it’s probably quite common).

Thanks for reading.

Answer 1

From the Flask.process_response docs:

Can be overridden in order to modify the response object before it’s sent to the WSGI server.

The response object is created on flask dispacher mechanism (Flask.full_dispatch_request). So if you want to create response objects under your own way, override Flask.make_reponse. Use Flask.process_response only when the desired modifications can be made using the created response object parameter.