Try,Except,Else to check that user has entered either y or n (Code block pasted)

[buran]

there is no error raised on this line reply = str(input("Do you want another drink Y/N ")), so except block is never executed and it jumps to else block. And input() returns str so there is no need to explicitly convert it with str(input("Do you want another drink Y/N "))

def ask():
    while True:
        reply = input("Do you want another drink Y/N ")
        if reply.lower() in ("y", "n"):
            print('you have correctly entered y or n')
            break
        else:
            print("you have incorrectly entered - pick Y/N")

ask()