singleton.py

# -*- coding: utf-8 -*-
"""
.. module:: openzwave.singleton

This file is part of **python-openzwave** project https://github.com/OpenZWave/python-openzwave.
    :platform: Unix, Windows, MacOS X
    :sinopsis: openzwave wrapper

.. moduleauthor:: bibi21000 aka Sébastien GALLET <bibi21000@gmail.com>

License : GPL(v3)

**python-openzwave** is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

**python-openzwave** is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with python-openzwave. If not, see http://www.gnu.org/licenses.

"""

class Singleton(type):
    """ Singleton metaclass
    """
    def __init__(self, *args, **kwargs):
        """ Init the metaclass
        @ivar __instances: instance of the class
        @type __instance: object
        """
        super(Singleton, self).__init__(*args, **kwargs)

        self.__instance = None

    def __call__(self, *args, **kwargs):
        if self.__instance is None:
            self.__instance = super(Singleton, self).__call__(*args, **kwargs)
        return self.__instance