On 05/23/2012 03:56 PM, Brett Cannon wrote: >
> On Wed, May 23, 2012 at 3:35 PM, PJ Eby <firstname.lastname@example.org
> <mailto:email@example.com>> wrote:
> On Wed, May 23, 2012 at 3:02 PM, Brett Cannon <firstname.lastname@example.org
> <mailto:email@example.com>> wrote:
> If I understand the proposal correctly, this would be a change
> in NamespaceLoader in how it sets __path__ and in no way affect
> any other code since __import__() just grabs the object on
> __path__ and passes as an argument to the meta path finders
> which just iterate over the object, so I have no objections to it.
> That's not *quite* the proposal (but almost). The change would also
> mean that __import__() instead passes a ModulePath (aka Nick's
> LazyIterable) instance to the meta path finders, which just iterate
> over it. But other than that, yes.
> And why does __import__() need to construct that? I thought
> NamespaceLoader was going to be making these "magical" __path__ objects
> that detected changes and thus update themselves as necessary and just
> stick them on the object. Why specifically does __import__() need to
> play a role?
Assume that we're talking about importing either a top-level namespace
package named 'parent' and a nested namespace package parent.child.
The problem is that NamespaceLoader is just passed the parent path
(typically sys.path, but if a sub-package then parent.__path__). The
concern is that if the parent path object is replaced:
sys.path = sys.path + ['new-dir']
parent.__path__ = ['new-dir']
then the NamespaceLoader instance can no longer detect changes to
So the proposed solution is for NamespaceLoader to be told the name of
the parent module ('sys' or 'parent') and the attribute name to use to
find the path ('path' or '__path__').
Here's another suggestion: instead of modifying the finder/loader code
to pass these names through, assume that we can always find
(module_name, attribute_name) with this code:
parent, dot, me = module.__name__.rpartition('.')
if dot == '':
return 'sys', 'path'
return parent, '__path__' >>> import glob
('sys', 'path') >>> import unittest.test.test_case
I guess it's a little more fragile than passing in these names to
NamespaceLoader, but it requires less code to change.
I think I'll whip this up in the pep-420 branch.
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