This version is included in macOS for compatibility with legacy software. Future versions of macOS will not include Python 2.7. Instead, it is recommended that you transition to using 'python3' from within Terminal. code example
Example 1: how to set default python version in macos
ln -s -f /usr/local/bin/python3.7 /usr/local/bin/pythonExample 2: set python3 as default mac
# it is said not to do but I used it anyway, because of the conveniency
$ echo "alias python=/usr/local/bin/python3.7" >> ~/.zshrc