On Tue, Mar 25, 2014 at 3:50 PM, Barry Warsaw <barry@python.org> wrote:

On Mar 25, 2014, at 03:35 PM, PJ Eby wrote:

>I think the correct fix would be to change the nspkg.pth magic to check for
>PEP 420 support, but unfortunately it seems we may have to use version
>checking: on rereading PEP 420 I see there's no 'sys.namespace_packages' or
>similar object that can be directly checked for feature support. :-(

There is. It's *pronounced* sys.namespace_packages, but it's spelled
importlib._bootstrap._NamespaceLoader ;)

Yeah, well that's not exactly a public attribute, so it's not necessarily a great way to do it. But if we did use that, presumably it'd add something like:

hnp = hasattr(sys.modules.get('importlib._bootstrap',None),'_NamespaceLoader');

To the front of the magic, and then prefix all subsequent expression values with 'not hnp and' in order to prevent them executing if PEP 420 support is available. (Note: it's checking sys.modules since on any interpreter where PEP 420 is natively available, the module should *already* be loaded by the time site.py does its thing.)

And we should probably think about adding sys.namespace_packages or something of the sort, or at least a proper flag for whether PEP 420 support is available on the platform.