How to get rid of global variables in a flask server code?

Question

While writing a flask server I find myself in a situation similar to this:

from flask import Flask, jsonify

app = Flask(__name__)
x = 0

@app.route('/method_a', methods=['GET'])
def method_a():
    global x
    x = x + 1
    return jsonify({'mesaage': 'value of x incremented by 1 is: '+str(x)}), 200

@app.route('/method_b', methods=['GET'])
def method_b():
    global x
    x = x + 2
    return jsonify({'message': 'value of x increased by 2 is: '+str(x)}), 200

Here, I have two methods which I am trying to invoke through GET requests from clients. So, when a single client makes 2 requests to '/method_b', the output should be 4, and so on. Now my problem is that, when the server will run in the real web, multiple clients will try to invoke its methods. So if first client invokes '/method_a' once, he gets output 1, meanwhile other clients will also invoke the methods, thus, changing the value of x. Thus when first client will make its 2nd request on '/method_a', it will not get the output as 2.
But I want to make a server which treats the variable values as different for different clients and show them only their version of the variable values. I am using global variables because both the methods need this variable to function, and since they are invoked by a GET request, I can't pass the value of variable through client. How to approach this problem? Is there a better way to write this code to addres the above problem?

You could have the client return their current value for `x` with the get request. E.g `/method_a?current=2`. That way your not storing state server side. — SuperShoot, Mar 22 '19 at 11:38

score 0 · Answer 1 · answered Mar 22 '19 at 12:53

If I understand it correctly, you can achieve this using cookies. Change the code of your view function to set the cookie in response:

@app.route('/method_a', methods=['GET'])
def method_a():
    x = request.cookies.get('xcookie', 0)
    x = x + 1
    response = jsonify({'mesaage': 'value of x incremented by 1 is: '+str(x)})
    response.set_cookie('xcookie', x)
    return response

How to get rid of global variables in a flask server code?

1 Answers1