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- import dataclasses
- class Singleton(type):
- _instances: dict = {}
- def __call__(cls, *args, **kwargs):
- if cls not in cls._instances:
- cls._instances[cls] = super(Singleton, cls).__call__(*args, **kwargs)
- else:
- # allow updates, just update existing instance
- # perhaps not the most orthodox way to do it, though it simplifies client code
- # useful for pre-defined groups of settings
- instance = cls._instances[cls]
- for key, value in kwargs.items():
- setattr(instance, key, value)
- return cls._instances[cls]
- @classmethod
- def reset(cls):
- # used by pytest to reset the state of the singleton instances
- for instance_type, instance in cls._instances.items():
- print('resetting... ', instance_type)
- for field_info in dataclasses.fields(instance_type):
- if dataclasses.is_dataclass(field_info.type):
- setattr(instance, field_info.name, field_info.type())
- elif field_info.default_factory is not dataclasses.MISSING:
- setattr(instance, field_info.name, field_info.default_factory())
- else:
- setattr(instance, field_info.name, field_info.default)
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