If you use a server framework like DjanGo, Express.js etc.. Nice. You can just search for [Framework Name] hot reload docker
and there will be plenty answers.
But if you use pure python scripts, that feature is not readily available, nor does docker suppports this feature despite being requested since 2014(cite needed. there is an open github issue)
So one way is to use docker volumes. just attach your local source code folder to container's source code folder, and changes will be applied instantly. ex../src:/app/src
Note it might not work if python interpreter is running the script actively ex.python src/app.py
, then changes to app.py might not be applied through docker volumes