[Python-Dev] PEP 520: Ordered Class Definition Namespace (original) (raw)

Terry Reedy tjreedy at udel.edu
Wed Jun 8 18:22:22 EDT 2016

On 6/8/2016 4:07 AM, Victor Stinner wrote:

Abstract ========

This PEP changes the default class definition namespace to OrderedDict. Furthermore, the order in which the attributes are defined in each class body will now be preserved in type._definitionorder_. This allows introspection of the original definition order, e.g. by class decorators. Note: just to be clear, this PEP is not about changing _dict_ for classes to OrderedDict. What is the cost in term of performance? What can be slower: define a new class and/or instanciate a class?

A class is defined once, used many times to instantiate instances. Each instance is typically used many times, with many lookups. So it is self.class_attribute lookups, like method lookups, that likely matter the most, and which are not changed by the PEP.

-- Terry Jan Reedy

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