Global variable get undefined on re-run of Flask app

global variables get undefined on re-run of flask app,I have 3 files,

api.py

import trainerapp = Flask(__name__)@app.route('/start', methods=['POST'])def apifunc(id):   result = trainer.consume(id)   return jsonify(result)if __name__ == '__main__':    app.run(debug=True, port=LISTEN_PORT, threaded=True, use_reloader=False)

trainer.py

from utilities import function1def consume(id)  value = function1(agg1)  ... some codes...  return value

utilities.py

aggregate = 30def function1(agg1):  global aggregate  ... some codes...  print(aggregate)  

when we run the app for the first time and hit the end point "/start", it picks the global variable "aggregate" value, it works,

buton 2nd hit, it throws error,

ERROR:api:500 Internal Server Error: name 'aggregate' is not defined

but when I stop and re-start the app and hit end point it works. Not sure why that's happening.