How to use 'pyenv' to manage multiple python versions?
'pyenv' is a tool that allows you to easily switch between multiple versions of Python.
Example:
Error: python3.9: version not installed
Solution:
1. Install 'pyenv' using Homebrew or from GitHub.
2. Use 'pyenv install 3.9.1' to install a specific version.
3. Use 'pyenv global 3.9.1' to set the default version.