SF bug [#469732] os.path.walk docstring inconsistent.
We have 5 implementations of walk(), and 5 different docstrings.  Combined
'em.  Let's see how long it takes before they're all different again!
diff --git a/Lib/ntpath.py b/Lib/ntpath.py
index a1baf83..ed8a2dd 100644
--- a/Lib/ntpath.py
+++ b/Lib/ntpath.py
@@ -291,11 +291,20 @@
 # or to impose a different order of visiting.
 
 def walk(top, func, arg):
-    """Directory tree walk whth callback function.
+    """Directory tree walk with callback function.
 
-    walk(top, func, arg) calls func(arg, d, files) for each directory d
-    in the tree rooted at top (including top itself); files is a list
-    of all the files and subdirs in directory d."""
+    For each directory in the directory tree rooted at top (including top
+    itself, but excluding '.' and '..'), call func(arg, dirname, fnames).
+    dirname is the name of the directory, and fnames a list of the names of
+    the files and subdirectories in dirname (excluding '.' and '..').  func
+    may modify the fnames list in-place (e.g. via del or slice assignment),
+    and walk will only recurse into the subdirectories whose names remain in
+    fnames; this can be used to implement a filter, or to impose a specific
+    order of visiting.  No semantics are defined for, or required of, arg,
+    beyond that arg is always passed to func.  It can be used, e.g., to pass
+    a filename pattern, or a mutable object designed to accumulate
+    statistics.  Passing None for arg is common."""
+
     try:
         names = os.listdir(top)
     except os.error: