install python3

Shell
sudo apt install build-essential zlib1g-dev libncurses5-dev libgdbm-dev libnss3-dev libssl-dev libreadline-dev libffi-dev wget
curl -O https://www.python.org/ftp/python/3.7.4/Python-3.7.4.tar.xz
tar -xf Python-3.7.4.tar.xz
cd Python-3.7.4
./configure --enable-optimizations
make
sudo make altinstall
python3.7 --version
cd ../https://www.python.org/ftp/python/3.8.2/python-3.8.2.exeYou cannot just pip install python3 because it is not a library.

If you want to install the latest python3:
https://www.python.org/ftp/python/3.8.2/python-3.8.2.exe # For macs... 
#  Apparently you don't want to upgrade 2.* just install 3.*

% brew install python3
Source

Also in Shell: