mac /usr/bin/python3 upgrade code example
Example 1: how to set default python version in macos
ln -s -f /usr/local/bin/python3.7 /usr/local/bin/python
Example 2: mac why is python installed in usr and application
$ pyenv global 3.7.3
# and verify it worked
$ pyenv version
3.7.3 (set by /Users/mbbroberg/.pyenv/version)