Source code for asab.abc.singleton
[docs]class Singleton(type):
"""
The `singleton pattern <https://en.wikipedia.org/wiki/Singleton_pattern>`_ is a software design pattern that restricts the instantiation of a class to one object.
*Note*: The implementation idea is borrowed from "`Creating a singleton in Python <https://stackoverflow.com/questions/6760685/creating-a-singleton-in-python>`_" question on StackOverflow.
"""
_instances = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]
[docs] @classmethod
def delete(cls, singleton_cls):
'''
The method for an intentional removal of the singleton object.
It shouldn't be used unless you really know what you are doing.
One use case is a unit test, which removes an Application object after each iteration.
'''
del cls._instances[singleton_cls]