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Python SQLAlchemy Basics Working with SQLAlchemy Creating Our Book Database

Andy McDonald
Andy McDonald
5,016 Points

How to identify empty query object when empty query is truthy?

Working on the project and if the app searches for a book thats not in the database I would like the app to say so. The best way I know how to do so is like so:

def delete():
    todel = input("What's the title of the book you want to delete?")
    dellie = models.session.query(models.Book).filter_by(title=todel)
    if dellie:
        for book in dellie:
            models.session.delete(book)
            models.session.commit()
            print('Alright that book is gone. Now what?')
    else:
        print('Cant find a book by that name. Try again.')

However, when I input a book title that does not exist it returns a query object that is truthy. Any suggestions?

[MOD: added ```python formatting -cf]

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 67,763 Points

Hey Andy McDonald, then query method count() gives the size of the query result.

    if dellie.count() > 0:

    # OR in truthy fashion

    if dellie.count():

Post back if you need more help. Good luck!!!