Here is a quick guide on installing Python3 on a mac

Installation

brew update
brew upgrade
sudo mkdir -p /usr/local/Frameworks
sudo chown -R $(whoami) /usr/local/* 
brew install python3
brew link python3
brew doctor
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Aliasing

 echo "alias python=/usr/local/bin/python3.7" >> ~/.zshrc
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or

echo "alias python=/usr/local/bin/python3.7" >> ~/.bashrc
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You could probably have just done this as well

alias python='python3'
alias pip='pip3'
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I hope this is useful