class astropy.utils.misc.OrderedDescriptor(*args, **kwargs)[source]

Bases: object

Base class for descriptors whose order in the class body should be preserved. Intended for use in concert with the OrderedDescriptorContainer metaclass.

Subclasses of OrderedDescriptor must define a value for a class attribute called _class_attribute_. This is the name of a class attribute on the container class for these descriptors, which will be set to an OrderedDict at class creation time. This OrderedDict will contain a mapping of all class attributes that were assigned instances of the OrderedDescriptor subclass, to the instances themselves. See the documentation for OrderedDescriptorContainer for a concrete example.

Optionally, subclasses of OrderedDescriptor may define a value for a class attribute called _name_attribute_. This should be the name of an attribute on instances of the subclass. When specified, during creation of a class containing these descriptors, the name attribute on each instance will be set to the name of the class attribute it was assigned to on the class.


Although this class is intended for use with descriptors (i.e. classes that define any of the __get__, __set__, or __delete__ magic methods), this base class is not itself a descriptor, and technically this could be used for classes that are not descriptors too. However, use with descriptors is the original intended purpose.