archey4/archey/singleton.py

22 lines
740 B
Python

"""Simple singleton meta-class definition"""
from abc import ABCMeta as AbstractBaseMetaClass
from typing import Dict
class Singleton(AbstractBaseMetaClass):
"""
Taken from : <https://stackoverflow.com/q/6760685/10599709>
This meta-class allows us to declare `Configuration` as a singleton.
This way, we are able to import `Configuration` in multiple modules, ...
... whereas it is effectively loaded only once.
You cannot instantiate this meta-class directly.
"""
_instances: Dict["Singleton", object] = {}
def __call__(cls, *args, **kwargs):
if cls not in cls._instances:
cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
return cls._instances[cls]