Python Collections ABC

lazy_loaded_list.py

import collections

class LazyLoadedList(collections.Sequence):

    def __init__(self, url):
        self.url = url
        self.page = 0
        self.num_items = 0
        self.store = []

    def load_data(self):
        data = requests.get(self.url, params={
            'page': self.page,
        }).json()
        self.num_items = data['total']
        objects = data.get('objects', [])
        self.store += objects
        return len(objects)

    def __getitem__(self, index):
        while index >= len(self):
            self.page += 1
            if not self.load_data():
                break
        return self.store[index]

    def __len__(self):
        return self.num_items

list_based_set.py

import collections

class ListBasedSet(collections.MutableSet):
    store = None

    def __init__(self, items):
        self.store = list(items) or []

    def __contains__(self, item):
        return item in self.store

    def __iter__(self):
        return iter(self.store)

    def __len__(self):
        return len(self.store)

    def add(self, item):
        if item not in self.store:
            self.store.append(item)

    def discard(self, item):
        try:
            self.store.remove(item)
        except ValueError:
            pass