{"id":8367,"date":"2025-09-05T07:19:46","date_gmt":"2025-09-05T07:19:46","guid":{"rendered":"https:\/\/studysection.com\/blog\/?p=8367"},"modified":"2025-09-05T07:29:15","modified_gmt":"2025-09-05T07:29:15","slug":"memento-pattern-in-python-with-examples","status":"publish","type":"post","link":"https:\/\/studysection.com\/blog\/memento-pattern-in-python-with-examples\/","title":{"rendered":"Memento Pattern in Python with Examples"},"content":{"rendered":"

The Memento pattern in Python<\/a> is a behavioral design pattern that captures and restores an object’s state without violating its encapsulation. This pattern is particularly useful when implementing undo mechanisms or managing the history of changes in an application.<\/p>\n

Let’s delve into the essence of the Memento pattern with a Python example:<\/strong><\/p>\n

 class Originator:\r\n    def __init__(self):\r\n        self._state = None\r\n\r\n    def set_state(self, state):\r\n        print(\"Setting state to:\", state)\r\n        self._state = state\r\n\r\n    def create_memento(self):\r\n        return Memento(self._state)\r\n\r\n    def restore_from_memento(self, memento):\r\n        self._state = memento.get_state()\r\n        print(\"State restored to:\", self._state)\r\n\r\n\r\nclass Memento:\r\n    def __init__(self, state):\r\n        self._state = state\r\n\r\n    def get_state(self):\r\n        return self._state\r\n\r\n\r\nclass Caretaker:\r\n    def __init__(self):\r\n        self._mementos = []\r\n\r\n    def add_memento(self, memento):\r\n        self._mementos.append(memento)\r\n\r\n    def get_memento(self, index):\r\n        return self._mementos[index]\r\n\r\n\r\n# Example usage\r\noriginator = Originator()\r\ncaretaker = Caretaker()\r\n\r\noriginator.set_state(\"State 1\")\r\ncaretaker.add_memento(originator.create_memento())\r\n\r\noriginator.set_state(\"State 2\")\r\ncaretaker.add_memento(originator.create_memento())\r\n\r\noriginator.set_state(\"State 3\")\r\ncaretaker.add_memento(originator.create_memento())\r\n\r\n# Restore to the previous state\r\noriginator.restore_from_memento(caretaker.get_memento(1)) <\/code><\/pre>\n
In this example, we have three main components:<\/p>\n