python flask request hook

You may be looking for flask.Flask.before_request.

Also you won't necessarily be able to add data into the request attributes form and args as they are immutable, consider using g which is a thread local.

Example usage:

from flask import Flask, request, g

app = Flask(__name__)

@app.route('/')
def home():
    return g.target + '\n'

@app.before_request
def before_req():
    g.target = request.args.get('target', 'default')

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

Usage:

$ wget -qO - 'http://localhost:5000/?target=value'
value
$ wget -qO - 'http://localhost:5000/?key=value'
default