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'''
Task Coach - Your friendly task manager
Copyright (C) 2004-2014 Task Coach developers <developers@taskcoach.org>
Task Coach 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.
Task Coach 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, see <http://www.gnu.org/licenses/>.
'''
class Singleton(type):
''' Singleton metaclass. Use by defining the metaclass of a class Singleton,
e.g.: class ThereCanBeOnlyOne:
__metaclass__ = Singleton
'''
def __call__(class_, *args, **kwargs):
if not class_.hasInstance():
# pylint: disable=W0201
class_.instance = super(Singleton, class_).__call__(*args, **kwargs)
return class_.instance
def deleteInstance(class_):
''' Delete the (only) instance. This method is mainly for unittests so
they can start with a clean slate. '''
if class_.hasInstance():
del class_.instance
def hasInstance(class_):
''' Has the (only) instance been created already? '''
return 'instance' in class_.__dict__
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