###Singleton Decorator Library
A decorator based on wiki.python.org Python Decorators Library, namely
https://wiki.python.org/moin/PythonDecoratorLibrary#Singleton, with significant
improvements.
Features (assuming you decorate a class definition of MyClass)
* Every call of MyClass() results in the same instance, which persists from the first instantiation until the end of execution
* Even if you delete all your references to the instance, it still persists to be returned on the next call of MyClass()
* That instance is only initiallized once (the first time)
* is_instance(MyClass(), MyClass) is True (that is, we do not wrap the class)
* Using copy() or deepcopy() simply gives another reference to the single instance
* The overhead of locking in the threaded version is low enough that you may use it even before adding threading to your class.
* If MyClass is threadsafe, then annotating with @threaded_singleton will give a threadsafe singleton (only the safety of creating the first instance requires locking, as all other singleton actions are no-ops or simply return a reference to the single instance)
* If MyClass has locking (either Lock or RLock) in the initialization (new and init) the singleton locking does not deadlock.
* The test suite is included, so you can tell if I verified correctly
* The singleton decorator and test bench pass black and mypy
* The test suite is automatically run before publishing
This has some fixes (correct calling of old init, correct replacement of init, removal of copy and deepcopy), plus a threadsafe version
from singleton_decorator1 import singleton
@singleton
class MyClass...
or
from singleton_decorator1 import threaded_singleton
@threaded_singleton
class MyThreadsafeClass...
Note that if MyThreadsafeClass is __not__ threadsafe, then the decorator
will not fix that -- it only ensures that the singleton functionality is
thread safe.
The library can be built with poetry >= 2.0:
[Recommended]
if needed, install pyenv
pyenv install 3.10
pyenv local 3.10
[required]
(pip show poetry | grep -q "Version: 2") || pip install --ignore installed poetry==2
poetry env use $(pyenv which python) or
poetry env use $(which python)
poetry install
poetry build
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"description": "###Singleton Decorator Library\n\nA decorator based on wiki.python.org Python Decorators Library, namely\nhttps://wiki.python.org/moin/PythonDecoratorLibrary#Singleton, with significant\nimprovements.\n\nFeatures (assuming you decorate a class definition of MyClass) \n* Every call of MyClass() results in the same instance, which persists from the first instantiation until the end of execution \n* Even if you delete all your references to the instance, it still persists to be returned on the next call of MyClass() \n* That instance is only initiallized once (the first time) \n* is_instance(MyClass(), MyClass) is True (that is, we do not wrap the class) \n* Using copy() or deepcopy() simply gives another reference to the single instance \n* The overhead of locking in the threaded version is low enough that you may use it even before adding threading to your class. \n* If MyClass is threadsafe, then annotating with @threaded_singleton will give a threadsafe singleton (only the safety of creating the first instance requires locking, as all other singleton actions are no-ops or simply return a reference to the single instance) \n* If MyClass has locking (either Lock or RLock) in the initialization (new and init) the singleton locking does not deadlock. \n* The test suite is included, so you can tell if I verified correctly \n* The singleton decorator and test bench pass black and mypy \n* The test suite is automatically run before publishing \n\nThis has some fixes (correct calling of old init, correct replacement of init, removal of copy and deepcopy), plus a threadsafe version\n\nfrom singleton_decorator1 import singleton \n@singleton \nclass MyClass... \n\nor\n\nfrom singleton_decorator1 import threaded_singleton \n@threaded_singleton \nclass MyThreadsafeClass... \n\nNote that if MyThreadsafeClass is __not__ threadsafe, then the decorator\nwill not fix that -- it only ensures that the singleton functionality is\nthread safe.\n\n\nThe library can be built with poetry >= 2.0: \n[Recommended] \nif needed, install pyenv \npyenv install 3.10 \npyenv local 3.10\n\n[required] \n(pip show poetry | grep -q \"Version: 2\") || pip install --ignore installed poetry==2\n\npoetry env use $(pyenv which python) or \npoetry env use $(which python)\n\npoetry install\n\npoetry build\n\n\n",
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