File size: 1,135 Bytes
8f59bb3 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 | class Singleton(type):
"""
Define an Instance operation that lets clients access its unique
instance.
"""
def __init__(cls, name, bases, attrs, **kwargs):
super().__init__(name, bases, attrs)
cls._instance = None
def __call__(cls, *args, **kwargs):
if cls._instance is None:
cls._instance = super().__call__(*args, **kwargs)
return cls._instance
class MyClass(metaclass=Singleton):
"""
Example class.
"""
pass
# class Singleton(object):
# _instance = None
# def __new__(cls, *args, **kwargs):
# if not isinstance(cls._instance, cls):
# print("Constructing singleton for", cls, 'with parameters', args, kwargs)
# # cls._instance = object.__new__(cls, *args, **kwargs)
# cls._instance = super(Singleton, cls).__new__(cls, *args, **kwargs)
# return cls._instance
# class Singleton(object):
# _instance = None
# def __new__(cls, *args, **kwargs):
# if not isinstance(cls._instance, cls):
# cls._instance = object.__new__(cls, *args, **kwargs)
# return cls._instance
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