2) d. None

Python also has a constant called “None” and it is used to indicate that an operation has produced no output. Sounds useless? You would be surprised how often “nothing” is used in Python or many other languages for that matter.

Sometimes you want a variable to hold no value. You cannot define it to hold 0 or “” because each of those are actually values. In this case you put “None” (without quotes) as the value.