PEP 3133 -- Introducing Roles

PEPs
1

I was looking if there was a way not to use method and property inheritance in python, as happens in Perl (Moose framework) with roles. I found this PEP but I didn’t find the real reason for its “rejected”. I tried to follow the guidelines of this project to create a module dedicated to roles, and this is the result: GitHub - MatteoGuadrini/pyrrole: Role system for Python3

I must say that it can be an alternative to the classic editing done with MRO. Can anyone tell me the reason why it was discarded?
Thanks

2

There’s a rejection notice at the top of the PEP:

The competitor PEP, PEP 3119, was accepted instead.
Commit: Accepting PEP 3119, rejecting its competitor PEP 3133. · python/peps@a2f9ba6 · GitHub

3

Another approach can be found in the zope.interface package. You might want to check that out if you’re not familiar with it.

-Fred

4

As for why roles weren’t considered necessary given ABCs: the ‘register’ mechanism provides the equivalent of dynamic role assignment, and keeping the existing “isinstance” and “issubclass” query mechanisms was considered preferable to requiring a new way of checking for desired functionality.