[Python-Dev] Strange artifacts with PEP 3121 and monkey-patching sys.modules (in csv, ElementTree and others) (original) (raw)

Antoine Pitrou solipsis at pitrou.net
Sun Aug 11 12:37:25 CEST 2013

On Sun, 11 Aug 2013 12:33:16 +0200 Antoine Pitrou <solipsis at pitrou.net> wrote:

So, the PEP 3121 "module state" pointer (the optional opaque void* thing) should only be used to hold non-PyObjects. PyObjects should go to the module dict, like they do in normal Python modules. Now, the reason our PEP 3121 extension modules abuse the module state pointer to keep PyObjects is two-fold:

1. it's surprisingly easier (it's actually a one-liner if you don't handle errors - a rather bad thing, but all PEP 3121 extension modules currently don't handle a NULL return from PyStateFindModule...) 2. it protects the module from any module dict monkeypatching. It's not important if you are using a generic API on the PyObject, but it is if the PyObject is really a custom C type with well-defined fields.

I overlooked a third reason which is performance. But, those lookups are generally not performance-critical.

Regards

Antoine.

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