Each version of Python installs to new folder.
You’ll have to download and install the new version of Python, and install any modules that you might have done via pip in your previous version.
You’ll have to take into account that some of your libraries won’t work in Python 3.6. A notable example would be Flask (currently, but that will change soon I’m sure.)
If you have virtual environments
In an ideal world anyway, you’d have a virtualenv for each of your projects, with a requirements.txt file that you can install from.
This makes it as easy as deleting your existing venv and recreating it from your requirements file within your project(s).
Couldn’t I just copy all my old libraries from my old install to the new one?
Yeah, in theory, you could. The most relevant folder would probably be PYTHONPATH/Lib/site-packages/, which I believe is the place where pip installs 3rd party libraries. You could copy all the libraries from in here, to your new install (in the same place). I can’t give any guarantee that you won’t run into bugs doing this, though.
But as I mentioned above, it’s way easier to just destroy your venv and create it again.
solved How can I update Python to 3.6.0? [closed]