How to run script by Execute via API?

Question

Python

There is a route to run the data parsing script

@app.get("/upload/")
async def upload():
    """ Загружаем список данных """
    return Parser

The Parser class has a script for connecting to the site, parsing it, and writing the received data to the database.

Through the request execution interface writes "Internal Server Error"
At the same time, when the server is restarted, the script automatically works.

I can not figure out how to make the script run exactly on request, and not when the server is restarted.