Check out my py code i need some help

Question

i created a py code. some guys helped me with some errors. but now i dont understand how to sole the latest occured error
https://code.sololearn.com/cExdOvdUx5UM/?ref=app

Answer 1

thank you

Answer 2

use letter == 'A'
all letters should be within either single or double quotes

Answer 3

check this

https://code.sololearn.com/cBfZcSFj3i8H/?ref=app