[FIXED] Parameter in route with Flask - local variable referenced before assignment

Issue

I'm trying to handle parameters in the routing path in Flask:

@app.route('/example/<id>', methods=['GET'])
def tasks(id):

    if id == 1:
        obj = FirstTask()
    elif id == 2:
        obj = SecondTask()
    elif id == 3:
        obj = ThirdTask()

    result = obj.start()
    
    return make_response(jsonify({ 'data': { result } }), 200)

After run, I get following error:

"local variable 'obj' referenced before assignment"

I've never programmed in Python and I don't know how to solve this.

Solution

You have two bugs, working in concert:

1. You're comparing apples to oranges, that is strings to integers.
2. You don't handle invalid ids.

The solution for the first is to add a converter to the route (int:), the solution for the second is to add an else:

from flask import abort

@app.route('/example/<int:id>', methods=['GET'])
def tasks(id):

    if id == 1:
        obj = FirstTask()
    elif id == 2:
        obj = SecondTask()
    elif id == 3:
        obj = ThirdTask()
    else:
        abort(404)

    result = obj.start()
    
    return make_response(jsonify({ 'data': { result } }), 200)

Answered By - Jasmijn