Iterator Design Pattern using Python

Iterator design pattern gives a way to access elements of a Collection in a sequential manner. It does not have to know the underlying working for the iteration to work.

Key Components:

1. Client - Class or function that contains a collection object and calls the next() method to access the collection items
2. Iterator Interface - Interface that defines the operations to ACCESS the collection items
3. Concrete Interface - Concrete class that implements the operations to ACCESS the collection items
4. Collection / Aggregator Interface - Interface that defines the operations to CREATE the collection
5. Concrete Collection / Aggregator - Concrete class that implements the operations to CREATE the collection

from abc import ABC

class IShoppingListIterator(ABC):
    def has_next(self):
        pass

    def next(self):
        pass


class IShoppingListCollection(ABC):
    def createIterator(self) -> IShoppingListIterator:
        pass


class ShoppingListIterator(IShoppingListIterator):
    def __init__(self, shopping_list: list[str]) -> None:
        self._shopping_list = shopping_list
        self._current_index = 0

    def has_next(self):
        return self._current_index < len(self._shopping_list)
            
    def next(self):
        current_item = self._shopping_list[self._current_index]
        self._current_index += 1
        return current_item
        

class ShoppingListCollection(IShoppingListCollection):
    def __init__(self, shopping_list) -> None:
        self._shopping_list = shopping_list

    def createIterator(self) -> IShoppingListIterator:
        return ShoppingListIterator(self._shopping_list)
    

def main():
    shopping_list = ["eggs", "apples", "butter"]
    aggregator = IShoppingListCollection(shopping_list=shopping_list)
    iterator = aggregator.createIterator()

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

main()        

Please find the notebook on Google Colab for a simple implementation of Iterator Design Pattern using #Python.?More implementations will be posted soon!

https://colab.research.google.com/github/penningjoy/designpatternswithpython/blob/main/Iterator_Design_Pattern.ipynb

Happy learning!

#softwaredevelopment #softwaredesignpatterns