linkedlist

import random


class _Node:
    def __init__(self, item):
        self.item = item
        self.next = None


class Bag:
    def __init__(self):
        self._head = None
        self._size = 0

    def __len__(self):
        return self._size

    def is_empty(self):
        return self._head is None

    def __contains__(self, item):
        current_node = self._head
        while current_node is not None and current_node.item != item:
            current_node = current_node.next
        return current_node is not None

    def add(self, item):
        new_node = _Node(item)
        new_node.next = self._head
        self._head = new_node
        self._size += 1

    def remove(self, item):
        previous_node = None
        current_node = self._head
        while current_node is not None and current_node.item != item:
            previous_node = current_node
            current_node = current_node.next
        if current_node is not None:                    # the item is found in Bag and Bag is not empty (!)
            if previous_node is None:                   # the item is in the head node
                self._head = current_node.next
            else:
                previous_node.next = current_node.next  # the item is not in the head node
            self._size -= 1
            del current_node
        else:                                           # the item is not found in Bag or Bag is empty (!)
            pass                                        # a null operation; nothing happens when it executes

    def __iter__(self):
        return _BagIterator(self._head)


class _BagIterator:
    def __init__(self, head):
        self._current_node = head

    def __iter__(self):
        return self

    def __next__(self):
        if self._current_node is not None:
            item = self._current_node.item
            self._current_node = self._current_node.next
            return item
        else:
            raise StopIteration


def main():
    my_bag = Bag()
    for i in range(20):
        random_int = random.randint(1, 100)
        my_bag.add(random_int)
        # print(random_int, end=' ')

    print()
    for item in my_bag:
        print(item, end=' ')

    print("\n", my_bag.is_empty())
    print()
    print(len(my_bag))

    print()
    # print(my_bag.remove(3))


if __name__ == '__main__':
    main()


class Node:
    def __init__(self, item):
        self.item = item
        self.item = None

class Bag:
    def __init__(self):
        self.head = None
        self.size = 0

    def __len__(self): # size() bag = Bag() len(bag)
        return self._size

    def add(self,item):
        new_node = Node(item)
        new_node.next = self.head
        self.head = new_node
        self.size += 1

    def size(self):
        return self.size()

    def is_empty(self):
        return self.size == 0

    def contains(selfs, item):
        current_node = self.head
        while current_node is not None and current_node.item != item:
            current_node = current_node.next

        return current_node is not None

    def remove(self, item):
        previous_node = None
        current_node = self._head
        while current_node is not None and current_node.item != item:
            previous_node = current_node
            current_node = current_node.next

        if current_node = None: pass
        else:
            self._size -= 1
            if previous_node is None:
                self.
                pass
            else current_node

    def __iter__(self):
        if self._index<(self._head.next)
            else