Where are all of the different Python Copies Installed? How can I find all of the different Python(s) installed on my Mac? I've accidentally damaged a copy of Python 3 that was under /usr/local/bin, and want to replace it/fix it, but I don't even know how Python 3 got there in the first place – macOS only ships with 2.7.

Can I use HomeBrew to fix a broken copy? 

How can I clean up my Python copies, so that I just have what should be there?
You can re-install the python3 that you messed up. With brew install python3  This linked question talks about the command line tools that may be need to complete the install. https://stackoverflow.com/questions/14583427/brew-install-python3-fails  

To remove the home-brew versions, so that you only have the system original 
brew remove python python3  &amp;&amp; brew cleanup