For building on macOS, you'll need Python 3. If you have Homebrew installed you likely already have it and "brew install python" in a Terminal window will ensure that you do. If you don't, go to https://brew.sh/, click the little clipboard icon under "Install Homebrew", paste (Command-V) it into a Terminal window and press Enter, and then follow the instructions. Once it's done, type "brew install python" and you're all set.