upgrade python 2.7 to 3.7 mac 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: 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

Example 3: 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)