New Instance Has Old Instance Attribute Values

I want to instantiate multiple instances of books. In my __init__() method I specify some default values. So I am expecting that every time I instantiate a new book, all the old va

Solution 1:

You should not use [] as default argument.

class Book(object):
    def __init__(self, title=None, book_rows=None):
        self.title = title
        self.book_rows = book_rows or []