# -*- coding: utf-8 -*- 

# lp4all: literate programming embedded in source code as wiki comments
# Copyright (C) 2006 Jean-Marie Favreau, Frédéric Lehobey, David Mentré
#                    and Thomas Petazzoni
# 
# This program 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 2 of the License, or
# (at your option) any later version.
# 
# This program 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 this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

Base class to implement the Singleton design pattern. It allows to ensure that derivative classes have only one instance. See Wikipedia for more information about the Singleton design pattern.

class Singleton:
    _singleton = None
    def getSingleton(cls):
        if not isinstance(cls._singleton, cls):
            cls._singleton = cls()
        return cls._singleton

    getSingleton = classmethod(getSingleton)