I need to call shutil.move() and be able to tell the
difference between an error such as access denied and
an error due to the two arguments being the same file.


--- old-dw/src/Lib/shutil.py    2006-05-22
00:06:02.000000000 -0300
+++ new-dw/src/Lib/shutil.py    2006-05-22
00:06:02.000000000 -0300
@@ -16,6 +16,9 @@
 class Error(exceptions.EnvironmentError):
     pass

+class SameFileError(Error):
+    pass
+
 def copyfileobj(fsrc, fdst, length=16*1024):
     """copy data from file-like object fsrc to
file-like object fdst"""
     while 1:
@@ -39,7 +42,7 @@
 def copyfile(src, dst):
     """Copy data from src to dst"""
     if _samefile(src, dst):
-        raise Error, "`%s` and `%s` are the same file"
% (src, dst)
+        raise SameFileError, "`%s` and `%s` are the
same file" % (src, dst)

     fsrc = None
     fdst = None

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Please apply.  This patch is completely backwards-compatible
and makes possible some uses of shutil.move().

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I'm not sure how to draw attention to my patch, so I will
try assigning it to anthonybaxter.  That ought to get attention.

Dear Pythonistas: please apply this patch.  There is no reason not to, and it enables programmers to use shutil more cleanly.

In order for patches to be applied, they require tests and doc updates as appropriate.  Can you supply these updates and attach a patch with all the changes?

@Zooko are you interested in taking this forward?

Antoine, is this obsoleted by PEP 3151?

I have re-read PEP 3151 and think it has no bearing on this bug: the PEP is about adding exception classes that map to errno values, and this report is about a library function that returns a custom exception unrelated to errnos.

I’m willing to review a patch with tests and docs updates for this, or write one myself.

This patch should fix the issue

Thanks for the patch.  I made a review on Rietveld; a mail should have been sent.

Thanks for the comments! Here'a a new patch.

Thanks, looks good.  There are a few minor cosmetic things I’ll change before committing.  I assume you have tested it on Windows?

My fault. I tested it only partially, relying on the documentation that says

"""
On Windows, if dst already exists, OSError will be raised even if it is a file
"""
Actually it does not (at least at my Windows 7):
(Pdb) os.path.isfile(src)
True
(Pdb) p os.rename(src, src)
None

Am I doing something wrong?

By testing, I mean running ./python -m test test_shutil

Yes, I got Windows 7, downloaded VS 2008 express, compiled, ran
python python_d.exe -m test test_shutil 
and tests failed. I found out that os.rename does not raise OSError, according to my previous comment...