During coding I came across with this simple recursion problem and I wrote an example of my code below. I ask somebody to find a good way to solve the problem. I guess it is supposed to write third class containing the relations.
from __future__ import annotations
from typing import Set
class Author:
def __init__(self):
self.books: Set[Book] = set()
def add_book(self, book: Book):
self.books.add(book)
book.add_author(self)
class Book:
def __init__(self):
self.authors: Set[Author] = set()
def add_author(self, author: Author):
self.authors.add(author)
author.add_book(self)
author = Author()
book = Book()
author.add_book(book) #RecursionError: maximum recursion depth exceeded while calling a Python object
The add_book() and add_author() methods call each other, so you get into an infinite loop.
The methods should check whether they're already added and not do anything, this will stop the recursion.
class Author:
def __init__(self):
self.books: Set[Book] = set()
def add_book(self, book: Book):
if book not in self.books:
self.books.add(book)
book.add_author(self)
class Book:
def __init__(self):
self.authors: Set[Author] = set()
def add_author(self, author: Author):
if author not in self.authors:
self.authors.add(author)
author.add_book(self)