Python singleton design pattern

example.py

from .singleton import Singleton

class Example(metaclass=Singleton):
    """
    Example class.
    """
    pass


def main():
    """ Main function """
    onj_1 = Example()
    obj_2 = Example()
    assert obj_1 is obj_2

if __name__ == '__main__':
    main()

singleton.py

"""
Singleton design pattern
"""

class Singleton(type):
    """ Singleton metaclass """

    def __init__(cls, name, bases, attrs, **kwargs):
        super().__init__(name, bases, attrs, **kwargs)
        cls._instance = None

    def __call__(cls, *args, **kwargs):
        if cls._instance is None:
            cls._instance = super().__call__(*args, **kwargs)
        return cls._instance