Flask Assign different ID to different website visitor at the same time and write their input information into json file - multithreading

Question

I am using FLASK to create a series of websites for doing a survey, I want to run the server once and invite multiple participants to help me fill the form on the webpage.
1.
I am aiming for assigning a unique ID (currently using python UUID) to different visitors and save their input info into different JSON files. (eg,. A's id is 00001, after he submiting the form, the info will be saved in the file named 00001.json, B's info will be saved in 00002.json). For now, I only create a UUID when the server start running, every visitor's information will be rewritten in the same file, (what I want is n visitors will produce n files).
2.
I want to show different survey questions to different visitors.
I am quite confused about if it is related to Multi-thread? Session? Cookie? Flask-login.
Hope someone can guide me on this. Thanks a lot!
assignmentID = str(uuid.uuid1())
jsonFileName = "upload/" + assignmentID + ".json"
jsonSurvey = "upload/" + assignmentID + "_survey.json"
#it ideally should randomly select different info/question no. to different user
Idx = random.sample(range(0,10), 5)
#app.route("/")
def index():
return render_template("surveyPage.html", data=Idx)
# write input information from webpage to JSON files, each visitor ideally should have their own JSON file.
#app.route("/record")
def recordData():
if request.method == 'POST':
print("READING FORM")
with open(jsonSurvey, 'w') as f:
json.dump(request.form, f)
f.close()
if __name__ == "__main__":
app.config['JSON_SORT_KEYS'] = False
app.run(debug = True)
# app.config["TEMPLATES_AUTO_RELOAD"] = True

Answer 1

You are defining assignmentID, jsonFileName, jsonSurvey and Idx outside of the request handlers which means they will be set once: when the server starts. jsonSurvey will therefore have the same value for each request which means that every new survey you store will overwrite the previous one.
The solution is to move the definition into the request handlers so that you genereate new values on each request.
#app.route("/")
def index():
Idx = random.sample(range(0,10), 5)
return render_template("surveyPage.html", data=Idx)
#app.route("/record")
def recordData():
if request.method == 'POST':
assignmentID = str(uuid.uuid1())
jsonFileName = "upload/" + assignmentID + ".json"
jsonSurvey = "upload/" + assignmentID + "_survey.json"
print("READING FORM")
with open(jsonSurvey, 'w') as f:
json.dump(request.form, f)
f.close()