QUERY · ISSUE

Method Resolution Order (MRO) is not compliant

openby pfalconopened 2014-04-28updated 2024-08-28

py-core

uPy currently implements depth-first MRO, which is equivalent to one used pre-Python2.2.
References:

http://python-history.blogspot.com/2010/06/method-resolution-order.html
https://www.python.org/download/releases/2.3/mro/

CANDIDATE · ISSUE

RFC: class.mro() is notimpl

openby pmp-popened 2019-09-13updated 2019-09-27

rfcpy-core

https://docs.python.org/3.5/library/stdtypes.html#class.mro

Lack of it can be annoying for writing proxy objects, missing .__bases__ and no mro() means no access to class hierachy at runtime for user defined classes.

Assessment

Q Qwen · high

Issue #525 reports that MicroPython's MRO implementation is incorrect (using depth-first instead of C3 linearization), which is a core bug in the method resolution algorithm itself. Issue #5106 requests a feature to expose the MRO via class.mro() for runtime introspection. While both issues concern MRO, they address fundamentally different problems: #525 is about fixing the underlying algorithm, while #5106 is about adding an API to access the MRO. Fixing #5106 (adding the mro() method) would not resolve #525 (the incorrect MRO algorithm). The issues are related by topic but one does not resolve the other.

Suggested action

Keep both issues open. #525 should be prioritized as it affects the correctness of multiple inheritance. #5106 can be addressed after or independently of fixing the MRO algorithm.

Method Resolution Order (MRO) is not compliant

RFC: class.mro() is notimpl

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