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Specify import hook support.

This commit is contained in:
Martin v. Löwis 2010-07-22 16:29:04 +00:00
parent cb5f8f7831
commit b200983097
1 changed files with 48 additions and 6 deletions
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54
pep-0382.txt
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@ -114,6 +114,12 @@ also want to extend __path__). At most one such asterisk gets
prepended to the path. In addition, the (possibly dotted) names of all
namespace packages are added to the set sys.namespace_packages.
If the first directory found on the path only contains an __init__.py
and no \*.pth file, searching the path stops; IOW, namespace packages
must include at least one .pth file. If both \*.pth files and an
__init__.py had been found, search continues looking for further
.pth files.
No other change to the importing mechanism is made; searching modules
(including __init__.py) will continue to stop at the first module
encountered. In summary, the process import a package foo works like
@ -121,13 +127,48 @@ this:
1. sys.path is search for a directory foo, or a file foo.<ext>.
If a file is found and no directory, it is treated as a module, and imported.
2. if it is a directory, it checks for \*.pth files. If it finds
any, a package is created, and its __path__ is extended.
3. The __init__ module is imported; this import will search the
__path__ that got computed already.
4. If neither a \*.pth file nor an __init__.py was found, the
2. if it is a directory, it checks for both \*.pth and an __init__ file. If it finds
only \*.pth files, a package is created, and its __path__ is extended.
3. If neither a \*.pth file nor an __init__.py was found, the
directory is skipped, and search for the module/package
continues.
continues. If an __init__.py was found, further search only looks
for \*.pth files.
4. If an __init__ module was found, it is imported, with __path__
being initialized to the path computed from the \*.pth files.
Impact on Import Hooks
----------------------
Both loaders and finders as defined in PEP 302 will need to be changed
to support namespace packages. Failure to comform to the protocol
below might cause a package not being recognized as a namespace
package; loaders and finders not supporting this protocol must raise
AttributeError when the functions below get accessed.
Finders need to support looking for \*.pth files in step 1 of above
algorithm. To do so, a finder must support a method:
finder.find_path(fullname, path=None)
This method will be called in the same manner as find_module, and it
must return a list of strings, each representing the contents of one
\*.pth file. If fullname is not found, is not a package, or does not
have any \*.pth files, None must be returned.
If any \*.pth files are found, but no loader was returned from
find_module, a package is created and initialized with the path.
If a loader was return, but no \*.pth files, load_module is called
as defined in PEP 302.
If both \*.pth files where found, and a loader was returned, a new
method is called on the loader:
loader.load_module_with_path(load_module, path)
where the path parameter is the list of strings containing the
contents of all \*.pth files.
Discussion
==========
@ -159,6 +200,7 @@ having users and tools starting to special-case 2.7). Prospective
users of this feature are encouraged to comment on this particular
question.
Copyright
=========