What does tty device means ?

Question

The python interpreter operates somewhat like the Unix shell: when called with standard input connected to a tty device, it reads and executes commands interactively; when called with a file name argument or with a file as standard input, it reads and executes a script from that file.

Answer 1

It is the command line interface for the Unix based systems.You have to type the command to run your python script.
>> python file_name

Answer 2

tty stand for TeleTYpewriter: that's the common name used to talk about virtual console/terminal wich you can access on unix/linux systems (I guess that apply too to OSx as based on unix/linux architecture -- kind of proprietary linux distribution)

that's also a unix command related to outputing to terminal/console: https://en.m.wikipedia.org/wiki/Tty_(unix)