[Python-Dev] Choosing a best practice solution for Python/extension modules

[Brett Cannon]

On Mon, Feb 23, 2009 at 04:02, Nick Coghlan <ncoghlan at gmail.com> wrote:

> Brett Cannon wrote:
> > I don't want to move it because this isn't some idea for a new feature
> > that may or may not be useful; this isn't an "idea", it's needed.
>
> It is needed, but it's only really needed in the test suite. The
> "sys.modules hackery" needed to get a Python-only version using the
> existing idiom really isn't that complicated and the associated import
> behaviour is perfectly well defined (putting a 0 in sys.modules may
> currently be a bit questionable, but I'd prefer to make sure that is
> officially supported with the desired effect rather than trying to
> define a new idiom for the actual library code for handling optional
> optimised extension modules).
>
> So, I'm still not seeing any significant problem with providing a
> utility function in test.support that hides that hackery and returns the
> pure Python version of the module.
>

Well, neither do I as your proposed approach below is what I do for
warnings. But I think you and I, Nick, are more comfortable with mucking
with imports than most people. =) I think some people early on in this
thread said they didn't like the idea of screwing around with sys.modules.
But doing that along with an import * from the extension module is probably
the simplest solution.

-Brett


>
> For example, a version that allows any number of extension modules to be
> suppressed when importing a module (defaulting to the Foo/_Foo naming):
>
>  import sys
>  def import_python_only(mod_name, *ext_names):
>    if not ext_names:
>        ext_names = (("_" + mod_name),)
>    orig_modules = {}
>    if name in sys.modules:
>      orig_modules[name] = sys.modules[name]
>      del sys.modules[name]
>    try:
>      for name in ext_names:
>        orig_modules[name] = sys.modules[name]
>        sys.modules[name] = 0
>      py_module = importlib.import_module(mod_name)
>    finally:
>      for name, module in orig_modules.items():
>        sys.modules[name] = module
>    return py_module
>
> Cheers,
> Nick.
>
> --
> Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
> ---------------------------------------------------------------
>
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