The Python3 command requires the command line developer tools. Would you like to install the tools now?

If you recently purchased a new Mac/Macbook or had a fresh installation of the latest macOS on your device (macOS Sonoma) you will see that when you run a python3 command on the Terminal you get a popup that says.

The "python3" command requires the command line developer tools. 

Would you like to install the tools now?

Choose Install to download and install the command line developer tools now.

Cancel    Install

This is because you need additional xcode-select tools are required to be installed on your system in order to run Python.

Code2care@Mac % python3

xcode-select: note: No developer tools were found, requesting install.
If developer tools are located at a non-default location on disk, use `sudo xcode-select --switch path/to/Xcode.app` 
to specify the Xcode that you wish to use for command line developer tools, and cancel the installation dialog.
See `man xcode-select` for more details.

So click install and follow the instructions in order to run Python on your Mac.