[Python-checkins] r53034 - sandbox/trunk/import_in_py/importer.py

[brett.cannon]

Author: brett.cannon
Date: Thu Dec 14 20:43:32 2006
New Revision: 53034

Modified:
   sandbox/trunk/import_in_py/importer.py
Log:
Pull out implementation notes out of the module docstring and move to the
Google Doc.

Also change exception messages to match.


Modified: sandbox/trunk/import_in_py/importer.py
==============================================================================
--- sandbox/trunk/import_in_py/importer.py	(original)
+++ sandbox/trunk/import_in_py/importer.py	Thu Dec 14 20:43:32 2006
@@ -1,115 +1,22 @@
 """Re-implementation of import machinery in Python source code.
 
+XXX See http://docs.google.com/View?docid=dg7fctr4_4d8tdbq on current status.
+
 References on import:
 * Language reference
-    http://docs.python.org/ref/import.html
+      http://docs.python.org/ref/import.html
 * __import__ function
-    http://docs.python.org/lib/built-in-funcs.html
+      http://docs.python.org/lib/built-in-funcs.html
 * Packages
-    http://www.python.org/doc/essays/packages.html
+      http://www.python.org/doc/essays/packages.html
 * PEP 235: Import on Case-Insensitive Platforms
-    http://www.python.org/dev/peps/pep-0235
+      http://www.python.org/dev/peps/pep-0235
 * PEP 275: Import Modules from Zip Archives
-    http://www.python.org/dev/peps/pep-0273
+      http://www.python.org/dev/peps/pep-0273
 * PEP 302: New Import Hooks
-    http://www.python.org/dev/peps/pep-0302/
+      http://www.python.org/dev/peps/pep-0302/
 * PEP 328: Imports: Multi-line and Absolute/Relative
-    http://www.python.org/dev/peps/pep-0328
-
-Clarifications
-==============
-* Raise ImportError when load_module() fails to load a module without
-  raising an exception.
-* Is module returned by load_module() actually used for anything?
-    + Can always just return from sys.modules.
-* PEP 302 does not mention if __name__ must be set before any code is executed
-  or not.
-
-
-XXX See http://docs.google.com/View?docid=dg7fctr4_4d8tdbq on current status.
-
-
-Things to be exposed at the Python level
-========================================
-* Python/marshal.c:r_long()/w_long()
-    + Using own version temporarily.
-
-
-Py3k
-====
-Improvements
-------------
-* Have a meta_path entry for checking sys.modules to remove need for
-  loaders or __import__ to do it.
-* Put importer objects directly into sys.path to remove need for
-  sys.path_importer_cache.  Could leave string entries on sys.path that do
-  not have an importer so they can be re-checked the next time a new import
-  is attempted.
-    + If __import__ handles sys.modules then the impact from having to
-      recheck sys.path entries that lack an importer is minimized as it is
-      only on imports that have not been handled before.
-        - This has the drawback of making it more difficult for
-          non-standard modules to be put into sys.modules.  Could go other
-          way and hyper-generalize by having a meta_path importer that
-          returns entries in sys.path.
-* Loaders don't have to return the loaded module.
-    + Importing the module being imported in a circular import dependency
-      requires that module added to sys.modules stay consistent from the
-      point it is added to initialization anyway.
-    + Can get the module the loader was supposed to handle directly out of
-      sys.modules.
-* Remove any idea of a default importer.
-    + Removes support for None entries from sys.path_importer_cache.
-    + Rely on default importers being in sys.path_hooks or sys.meta_path. 
-* Remove implicit relative import in packages when dealing with '*'.
-    + Would only require adding an import line for each item in __all__ that is
-      a module.
-    + Explicit is better than implicit.
-    + Can't entire remove without requiring ``import pkg.module as module``
-      on imports instead of ``from pkg import module``.
-* Any way to replace imp.acquire_lock()/release_lock() with a context manager instead?
-       
-Rejected Ideas
---------------
-* Passing in new module to loaders
-    Creating a new module is minimal and loader might want to use a different
-    type of object.
-
-
-Use Cases
-=========
-PTL
----
-* Use filesystem importer and loader.
-* Subclass PyPycHandler
-    + Set source_handles to '.ptl' and bytecode to '.ptlc'.
-    + code_from_source()
-        - Handle transforming to pure Python code here.
- 
-sqlite3
--------
-+ DB
-    - Module name.
-    - Source code.
-    - Marshalled code of the source.
-        * Set to NULL when source code is modified, which removes need of
-          storing the bytecode's timestamp.
-    - Magic number for bytecode.
-    - Anything about handling packages?
-+ Importer
-    - Query DB to see if module is listed.
-    - Whether it is in bytecode or source form is irrelevant.
-+ Loader
-    - See if bytecode is in DB; if so then have that used, otherwise source.
-    - Implement API needed by PyPycHandler for free bytecode recreation.
-+ Use PyPycHandler.
-
-zip importer
-------------
-+ New importer
-+ New loader
-    - Have write_data be a no-op.
-+ Reuse PyPycHandler.
+      http://www.python.org/dev/peps/pep-0328    
 
 """
 from __future__ import with_statement
@@ -587,7 +494,7 @@
             if loader:
                 return loader
         else:
-            raise ImportError("%s not found on sys.meta_path" % name)
+            raise ImportError("No module named %s" % name)
 
     def sys_path_importer(self, path_entry):
         """Return the importer for the specified path.
@@ -647,7 +554,7 @@
             if loader:
                 return loader
         else:
-            raise ImportError("%s not found on sys.path" % name)
+            raise ImportError("No module found named %s" % name)
             
     def import_module(self, name, path=None):
         """Import the specified module with no handling of parent modules.