How to run my python script only when new response form requests.get is received?

I wrote a application with the following logic:

1) Fetch Data with API2) Preprocess the Data3) Start topic modeling4) Create report and include data5) Handle final pdf report (send, show in browser ...)

Now i only want to start this 5 steps when a new response is received. 

So far the script works, but only processes the response when i manually run the script on my system.

I also tried using pm2 for running the script like a daemon thread. However, even the script (process) runs forever, it loops over the 5 steps over and over again for the same response. But i want to stop the 5 steps after every individual response.

My desired architecture should look like that:

if new response:    1) Fetch Data with API    2) Preprocess the Data    3) Start topic modeling    4) Create report and include data    5) Handle final pdf report (send, show in browser ...)else:    wait for new reponse …

Any help is appreciated.

EDIT in title* form not form