The term 'python' is not recognized as the name of a cmdlet, function, script file, or operable program code example

Example 1: 'python' is not recognized as an internal or external command

Did you add python to PATH when you downloaded it?
If not, redownload it and make sure you tick the box that says 'add Python to PATH'.

Example 2: python is not recognized as an internal or external command when running script

If when executing the python program you get this error, simply replace the word "python" with "py"
Instead of python first.py
Write py first.py