Where are all of the different Python Copies Installed?
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