iterator.py

from __future__ import annotations
from typing import Any, List, Optional

# Iterator interface
class Iterator:
 def __init__(self, collection: MyList):
 self._collection = collection
 self._index = 0

 def has_next(self) -> bool:
 return self._index < len(self._collection)

 def next(self) -> Optional[Any]: # getNext()
 if self.has_next():
 item = self._collection[self._index]
 self._index += 1
 return item
 else:
 return None

# Aggregate interface
class Aggregate:
 def create_iterator(self) -> Iterator: # createIterator()
 pass

# Concrete Aggregate
class MyList(Aggregate):
 def __init__(self):
 self._items: List[Any] = []

 def add_item(self, item: Any):
 self._items.append(item)

 def __getitem__(self, index: int) -> Any:
 return self._items[index]

 def __len__(self) -> int:
 return len(self._items)

 def create_iterator(self) -> Iterator: # createIterator()
 return Iterator(self)

# Client code
def client_code(collection: Aggregate):
 iterator = collection.create_iterator()

 while iterator.has_next():
 item = iterator.next()
 print(item)

# Usage
my_list = MyList()
my_list.add_item("Item 1")
my_list.add_item("Item 2")
my_list.add_item("Item 3")

client_code(my_list)

## Output
# Item 1
# Item 2
# Item 3