Logical error in while statement when used with or operator

Question

I've written the following block of code. The code is correct syntax wise but has some logical error that I can't find. The code takes in name, author and assigns a bool value to read based on user input. The while loop section has some logical error due to which the interpreter never get to while loop and hence add_book function fails as read has no value assigned.

name = input("Title: ").lower()
author = input("Author: ").lower()
has_read = input("Mark as Read (y/n): ").lower()
while has_read not in ['n', 'y']:
    if has_read == 'y':
        read = True
    else:
        read = False
    add_book(name, author, read)

Start with: "if has_read not in [n, y]: if has_read equals y"… How can it be not "y" and equal "y"…? — deceze
– deceze ♦, Commented Dec 10, 2018 at 13:50
Your while loop condition makes it impossible to enter the loop. You ask the user to input a y or a n, but you can only enter the loop if they entered something other than that! — Neil
– Neil, Commented Dec 10, 2018 at 13:51
I guess you want to re-ask the user to input something if you get something other than y or n. Once you get that answer you can exit the while loop and mark your book. — toti08
– toti08, Commented Dec 10, 2018 at 13:52
You probably want "while not y/n: ask user again", then afterwards do your if outside the while. — deceze
– deceze ♦, Commented Dec 10, 2018 at 13:52
Possible duplicate of Asking the user for input until they give a valid response — Patrick Artner
– Patrick Artner, Commented Dec 10, 2018 at 13:57

Morgan Saville · Accepted Answer · 2018-12-10 14:11:44Z

1

You'll probably need to re-ask the user if they don't give a valid input. Maybe something like this:

name = input("Title: ").lower()
author = input("Author: ").lower()
valid = False
while not valid:
    has_read = input("Mark as Read (y/n): ").lower()
    if had_read in ['n', 'y']:
        valid = True
        if has_read == 'y':
            read = True
        else:
            read = False
        add_book(name, author, read)

answered Dec 10, 2018 at 14:11

Morgan Saville

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