i making a terminal sign up website thing

[bowlofred]

Please use bbcode tags for your python code (you can press the python button above the editor).

if YesNo == f:

This code checks if the variable YesNo has the same value as the variable f. But since you haven't assigned to the variable f yet, this is an error. I suspect you wanted to check if it was the string f. If so, you need to use quotes to define the string.

if YesNo == "f":

It is also a good idea not to use the same name for both a function and a variable in the function. Because they have different scope, this won't break immediately. But there are situations where this would cause confusion. Better to pick different names:

def username():
    username = input("username:") #username used as function name and string name
    ...