120.py

"""
Problem:

Implement the singleton pattern with a twist. First, instead of storing one instance,
store two instances. And in every even call of getInstance(), return the first instance
and in every odd call of getInstance(), return the second instance.
"""

from __future__ import annotations


class Twisted_Singleton:
    _instance1, _instance2 = None, None
    _is_odd = True
    _is_initialized = False

    def __init__(self, instance_num: int) -> None:
        self.instance_num = instance_num

    def __repr__(self) -> str:
        return str(self.instance_num)

    @staticmethod
    def initialize() -> None:
        if not Twisted_Singleton._is_initialized:
            Twisted_Singleton._instance1 = Twisted_Singleton(1)
            Twisted_Singleton._instance2 = Twisted_Singleton(2)
            Twisted_Singleton._is_initialized = True

    @staticmethod
    def getInstance() -> Twisted_Singleton:
        if not Twisted_Singleton._is_initialized:
            Twisted_Singleton.initialize()

        if Twisted_Singleton._is_odd:
            instance = Twisted_Singleton._instance1
        else:
            instance = Twisted_Singleton._instance2
        Twisted_Singleton._is_odd = not Twisted_Singleton._is_odd
        return instance


if __name__ == "__main__":
    Twisted_Singleton.initialize()

    print(Twisted_Singleton.getInstance())
    print(Twisted_Singleton.getInstance())
    print(Twisted_Singleton.getInstance())
    print(Twisted_Singleton.getInstance())
    print(Twisted_Singleton.getInstance())
    print(Twisted_Singleton.getInstance())