44 lines
1.5 KiB
Python
44 lines
1.5 KiB
Python
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class ClassRegistry(type):
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"""Maintain a registry of classes, indexed by name.
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Note that this implementation requires that the names be unique, as it uses
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a dictionary to hold the classes by name.
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The name in the registry can be overridden via the 'name' attribute of the
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class, and the 'priority' attribute controls priority. The prioritized()
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method returns the registered classes in priority order.
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Subclasses of ClassRegistry may define an 'implemented' property to exert
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control over whether the class will be added to the registry (e.g. to keep
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abstract base classes out of the registry)."""
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priority = 0
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class __metaclass__(type):
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"""Give each ClassRegistry their own registry"""
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def __init__(cls, name, bases, attrs):
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cls.registry = {}
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type.__init__(cls, name, bases, attrs)
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def __init__(cls, name, bases, attrs):
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super(ClassRegistry, cls).__init__(name, bases, attrs)
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try:
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if not cls.implemented:
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return
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except AttributeError:
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pass
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try:
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cls.name
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except AttributeError:
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cls.name = name
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cls.registry[cls.name] = cls
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@classmethod
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def prioritized(tcls):
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return sorted(tcls.registry.values(),
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key=lambda v: v.priority, reverse=True)
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def unregister(cls):
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for key in cls.registry.keys():
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if cls.registry[key] is cls:
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del cls.registry[key]
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