Singleton decorator class.

singleton.py

#!/usr/bin/env python3
"""Singleton decorator class."""

class Singleton:
    def __init__(self, cls):
        self.__cls = cls
        self.__obj = None

    def __call__(self, *args, **kwargs):
        if not self.__obj:
            self.__obj = self.__cls(*args, **kwargs)
        return self.__obj

if __name__ == "__main__":
    # Testing ...

    @Singleton
    class Test:

        def __init__(self, text):
            self.text = text

    a = Test("Hello")
    b = Test("World")

    print("id(a):", id(a), "id(b):", id(b), "Diff:", id(a)-id(b))