how to change python version macos to 3.9 code example

Example 1: mac upgrade python to 3.8

brew install python3
brew update && brew upgrade python
alias python=/usr/local/bin/python3

Example 2: how to change mac default python version

$ echo -e 'if command -v pyenv 1>/dev/null 2>&1; then\n  eval "$(pyenv init -)"\nfi' >> ~/.zshrc