ptpython is an advanced python REPL that allows you to do an interactive coding session with extended functionality such as auto completion.
Some terms to help you navigate the post
An advanced REPL for python; Source.
An interactive coding environment. A REPL allows you to type code directly into a terminal (or webpage) and run code. This is incredibly useful for testing something small out in a language, or for teaching purposes.
To run ptpython you need to first install it, the easiest way is through pip
pip install ptpython or
pip3 install ptpython
ptpython (and REPL's more generally) are incredibly useful for testing small chunks of code and/or for teaching people with small snippets of code
ptpython has a huge number of extra features to the default python REPL such as autocompletion and multiline. See features docs for more details.