Modify request data before view functions in Flask API

Question

Is it an allowed pattern in Flask to modify request json data before the view functions (e.g. in a decorator)? Is it even possible? Imagining something like this:

from functools import wraps
from flask import request, current_app

def my_function_decorator(func):
    @wraps(func)
    def decorated_function(*args, **kwargs):
        req = request.get_json()
        # do something to calculate the new value
        req["new key"] = "new value"
        request.set_json(req)

        return func(*args, **kwargs)

    return decorated_function 

The purpose is to have lat lon data geocoded from a third party service, based on address data that is sent to my service. Not sure if decorators are the right choice for this, or if it is before_request, or something else, or nothing at all.

Answer 1

I know this is a very old question, but there are people who coming here from google (like me). The answer would be:

from functools import wraps
from flask import Flask

from werkzeug.datastructures import ImmutableMultiDict

def my_function_decorator(func):
    @wraps(func)
    def decorated_function(*args, **kwargs):
        http_args = request.args.to_dict()
        http_args ['Shered Data'] = 'Hi!'

        request.args = ImmutableMultiDict(http_args )

        return func(*args, **kwargs)

    return decorated_function 

server = Flask(__name__)

@server.route('/')
@my_function_decorator
def index():
    #Now, request.args contains your data
    return 'It works! Shared data: %s' % (request.args.get('Shered Data'))

server.run(debug=True)