chr()
requires an integer, but input()
returns a string. Just remove the chr()
call:
letter = input('Enter a letter').lower()
If you wanted to limit the input to just one character, use slicing:
letter = input('Enter a letter')[:1].lower()
Python doesn't have a 'single character' type.
chr()
is only used to turn an integer code point into a (single character) string:
>>> chr(65)
'A'