[Python-Dev] Change PEP 399 import recommendation (original) (raw)

Oscar Benjamin oscar.j.benjamin at gmail.com
Sun Oct 13 18:35:59 CEST 2013

On 12 October 2013 17:55, Christian Heimes <christian at python.org> wrote:

Am 12.10.2013 17:37, schrieb Nick Coghlan:

I think the default recommendation in PEP 399 still makes sense - 2 modules are easy to manage than three and the idiom allows for easy partial replacement. We could ues yet another approach and put the pure Python implementation of modules into another directory (e.g. Lib/pystdlib or Lib/purepython). This directory is appended to sys.path. Alternative implementations of Python or platforms without the necessary bits and pieces would import the Python-only version from that directory. C modules can be renamed so CPython picks them up in favor of the pure Python modules. No hacks, no facade module, no slow down and it's easy to understand, too. The approach can be used for stat, operator, decimal and perhaps other modules, too.

CPython preferentially imports extension modules over .py modules with the same name. This is what happens when you use Cython in "pure" mode: You have a pure mod.py file and an "augmenting" mod.pxd that contains the annotations relevant to Cython. The resulting extension module is mod.{pyd,so} and is imported by CPython if present. This way you don't need an additional directory/module.

Oscar

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