NameError x not defined

[Larz60+]

You should read the brief tutorial that ichabod801 shows above it will help
here's an example that might help:

>>> def choose_color(choice):
...     hue = ['red', 'yellow', 'green', 'blue']
...     return hue[choice]
... 
>>> def paint_my_car(color):
...     print('I will paint my car {}'.format(color))
... 
>>> paint_my_car(choose_color(0))
I will paint my car red
>>> paint_my_car(choose_color(2))
I will paint my car green
>>>