How to access the cookies database of firefox when firefox is running with python?

I want to access the cookies programmatically which are stored in the cookies database on the filesystem. I tried to use this code, but it either gives a message

database is locked

when the browser is running, or does not yield any results when the browser has been quit (I assume all cookies are removed on the filesystem then?).

How can I programmatically access all cookies related to a browser session with python? I want to have a script that e.g. lists all the cookies on a terminal. How to do that? (Can be either chrome or firefox).

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