[Python-checkins] python/nondist/peps pep-0302.txt,1.14,1.15

[pje at users.sourceforge.net]

Update of /cvsroot/python/python/nondist/peps
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv9906

Modified Files:
	pep-0302.txt 
Log Message:
It's PyImport_AddModule, not PyImport_ModuleAdd.  Fix Python code sample
to do the right thing for reload() to work.  Revise explanation so it's
clear what to do to fulfill reload()'s requirements in both C and Python.


Index: pep-0302.txt
===================================================================
RCS file: /cvsroot/python/python/nondist/peps/pep-0302.txt,v
retrieving revision 1.14
retrieving revision 1.15
diff -u -d -r1.14 -r1.15
--- pep-0302.txt	23 Sep 2004 04:06:40 -0000	1.14
+++ pep-0302.txt	23 Sep 2004 13:54:53 -0000	1.15
@@ -240,22 +240,27 @@
     The load_module() method has a few responsibilities that it must
     fulfill *before* it runs any code:
 
-    - It must use the existing module object from sys.modules, if one
-      exists.  (Otherwise, the reload() builtin will not work
-      correctly.)
+    - If there is an existing module object named 'fullname' in
+      sys.modules, the loader must use that existing module.
+      (Otherwise, the reload() builtin will not work correctly.)
+      If a module named 'fullname' does not exist in sys.modules,
+      the loader must create a new module object and add it to
+      sys.modules.
 
-    - If a module object is not already present in sys.modules, the
-      loader must create a module object.  From Python this can be done
-      via the new.module() function, the imp.new_module() function or
-      via the module type object; from C with the PyModule_New()
-      function or the PyImport_ModuleAdd() function.  The latter also
-      does the following step:
+      In C code, all of these requirements can be met simply by using
+      the PyImport_AddModule() function, which returns the existing
+      module or creates a new one and adds it to sys.modules for you.
+      In Python code, you can use something like:
 
-    - It must add the module to sys.modules, if it was not already
-      present there.  This is crucial because the module code may 
-      (directly or indirectly) import itself; adding it to sys.modules
-      beforehand prevents unbounded recursion in the worst case and
-      multiple loading in the best.
+        module = sys.modules.setdefault(fullname, new.module(fullname))
+
+      to accomplish the same results.
+
+      Note that the module object *must* be in sys.modules before the
+      loader executes the module code.  This is crucial because the
+      module code may (directly or indirectly) import itself; adding
+      it to sys.modules beforehand prevents unbounded recursion in the
+      worst case and multiple loading in the best.
 
     - The __file__ attribute must be set.  This must be a string, but it
       may be a dummy value, for example "<frozen>".  The privilege of
@@ -279,8 +284,7 @@
 
         def load_module(self, fullname):
             ispkg, code = self._get_code(fullname)
-            mod = imp.new_module(fullname)
-            sys.modules[fullname] = mod
+            mod = sys.modules.setdefault(fullname, imp.new_module(fullname))
             mod.__file__ = "<%s>" % self.__class__.__name__
             mod.__loader__ = self
             if ispkg: