[Python-Dev] PEP 487 vs 422 (dynamic class decoration) (original) (raw)

Martin Teichmann lkb.teichmann at gmail.com
Thu Apr 2 13:47:54 CEST 2015

Hi everyone,

for those new to the discussion, I am the author of PEP 487, which has been discussed here: https://mail.python.org/pipermail/python-ideas/2015-February/032249.html

The concern is twofold: it breaks proper information hiding/DRY, and it fails silently. It should not be necessary for clients of package A1 (that uses a decorator built using package B2) to mixin a metaclass or decorator from package C3 (because B2 implemented its decorators using C3), just for package A1's decorator to work properly in the client package's class. (And then, of course, this all silently breaks if you forget, and the breakage might happen at the A1, B2, or C3 level.)

I am just not capable to understand things at such an abstract level, would it be possible to give a simple example on what and how you did things in python 2?

IOW, there's no need to modify the core just to have that feature, since if you control the base class you can already do what PEP 487 does in essentially every version of Python, ever. If that's all PEP 487 is going to do, it should just be a PyPI package on a stdlib-inclusion track, not a change to core Python. It's not actually adding back any of the dynamicness (dynamicity? hookability?) that PEP 3115 took away.

That was my point. You can find the PyPI package at: https://pypi.python.org/pypi/metaclass

Greetings

Martin

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