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"""Sentinel class."""
__all__ = ('Sentinel', 'NOT_SET')
class Sentinel:
"""A class to create sentinel objects.
The benefits vs. object() are a good repr it is picklable.
Inspired by https://pypi.org/project/sentinels/
"""
_registry = {}
def __getnewargs__(self):
return self._name,
def __new__(cls, _name):
"""Find the Sentinel object with name or create a new one."""
try:
return cls._registry[_name]
except KeyError:
new = super(Sentinel, cls).__new__(cls)
cls._registry[_name] = new
return new
def __init__(self, name):
super(Sentinel, self).__init__()
self._name = name
def __repr__(self):
return '<%s>' % self._name
def __bool__(self):
return False
def __eq__(self, other):
if other.__class__ == self.__class__:
return self._name == other._name
return False
NOT_SET = Sentinel('not_set')
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