I understand how this was needed historically, when using the official installer might overwrite the Python you already had installed. But as far as I know, you can download an installer for a new version, run it, and it doesn't touch your previous installation.

For example I've had 3.7 on my macOS system for a while, installed from the official installer, not through Homebrew. I just installed 3.8, which pointed my python3 to 3.8. But my 3.7 was still there; I created an alias python3.7 to point to that. So I can run or install anything I want against 3.7 or 3.8.

Why do we still need pyenv? I'm not asking that antagonistically, I really don't understand at this point and I'm wondering if I'm missing something.

Sometimes scripts will want to invoke Python as ‘python’ and it’s easier to use pyenv to set $PATH overrides.

Thank you, that’s the first concrete reason I’ve heard. It also explains why I haven’t run into issues yet using my own aliases.

Why do you need pyenv to set PATH?

Maybe you don’t, but it’s a way of doing it.

Specifically, pyenv will dynamically and programmatically link the $PATH for the Python executables (python, pip, etc.) to the desired version as defined either by an environment variable or by the contents of a .python-version file in CWD or an ancestor thereof. The .python-version file can be checked into version control.

Honestly I haven’t used official installations before so I can’t speak to that too much. Pyenv mostly uses official builds though so it’s mostly an automated frontend to manual installs.

I like being able to specify the global and local versions for my projects and the system as a whole. I also use it as a virtualenv manager. It works well with pipenv (which I still use in anger) and vscode.