Python 3 Object-Oriented Programming - Third Edition

Extending built-ins

One interesting use of this kind of inheritance is adding functionality to built-in classes. In the Contact class seen earlier, we are adding contacts to a list of all contacts. What if we also wanted to search that list by name? Well, we could add a method on the Contact class to search it, but it feels like this method actually belongs to the list itself. We can do this using inheritance:

class ContactList(list):    def search(self, name):        """Return all contacts that contain the search value        in their name."""        matching_contacts = []        for contact in self:            if name in contact.name:                matching_contacts.append(contact)        return matching_contactsclass Contact:    all_contacts = ContactList()    def __init__(self, name, email): self.name ...