从字典里面附加一个列表？

Question

Attempting to add authors and their book titles to a list inside of a dictionary so that each author can support multiple book titles. In the code, I have 3 authors already and each has 1 book title, but they need to be able to support at least 1 more book title.

I have the values (book titles) of the keys (authors) nested inside of a list inside the dictionary already, but I don't know how to append more values to the existing keys that are inside of the existing list.

readings = {'George Orwell': ['1984'], 'Harper Lee': ['To Kill a Mockingbird'], 'Paul Tremblay': ['The Cabin at the End of the World']}  # list inside of dict.

I need to use the following code to append the new book titles to the list

def add(readings):  # appending to list will go here
    author = input('\nEnter an author: ')
    if author in readings:  # check if input already inside dict.
        bookTitle = readings[author]
        print(f'{bookTitle} is already added for this author.\n')
    else:
        bookTitle = input('Enter book title: ')
        bookTitle = bookTitle.title()
        readings[author] = bookTitle
        print(f'{bookTitle} was added.\n')

I expect that you are not able to add the same book title twice and not be able to add the same author twice either. I am expected to be able to input book titles for an existing author (or new author not already existing) while the program is running, then be able to view all of the authors and their book title(s) via a 'command menu' (not shown).

Answer 1

You're workflow is a little off. After checking for the author, then check for the book in the list of books by that author. You can add a title to the list of books using .append . Try this:

def add(readings):  # appending to list will go here
    author = input('\nEnter an author: ')
    if author in readings:  # check if input already inside dict.
        books = readings[author]
        print(f'Found {len(books)} books by {author}:')
        for b in books:
            print(f' - {b}')
    else:
        readings[author] = []

    bookTitle = input('Enter book title: ')
    bookTitle = bookTitle.title()

    if bookTitle in readings[author]:
        print(f'{bookTitle} is already added for this author.')
    else:
        readings[author].append(bookTitle)
        print(f'Add "{bookTitle}"')

Answer 2

So you are trying to add multiple books to an author, is that correct? Since the values in your dictionary are already stored as list, you can try doing -

readings[author].append(bookTitle)

instead of

readings[author] = bookTitle