Just installed Python 3.9.6. Firefox will now no longer open local .py files as plain text

Hi, everyone. Sorry if this is an inappropriate place to post this question.

Up until a few days ago, I could click a link to a locally stored .py file and Firefox would display it as a plain text file. This is what I want; e.g., it’s a way for me to organize notes, view examples I’ve created in the past, and like that.

Now when I click such a link, Firefox pops up a window asking me if I want to “Open with …” or “Save file”.

I installed Python 3.9.6 a few days ago, so I wondered it that was a coincidence. I don’t think it is, because I just went to another machine, where clicking a link to a .py file worked as desired, updated the Python on that machine, and now I’m seeing the same (unwanted) behavior.

I do have a question posted about this in the Mozilla support forum, but I thought I ought to mention this here, too. And ask if there is anything that’s new in the Python installation procedure that would cause this. And if so, is it something I could fix by re-installing Python and doing something different during the installation?

Thanks in advance for any suggestions.

P.S. Both machines are running Win 10 Pro, and both are running Firefox v90.0.2.