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Title: fix_import in 2to3 adds spurious relative import (windows)
Type: behavior Stage: resolved
Components: 2to3 (2.x to 3.x conversion tool) Versions: Python 3.3
Status: closed Resolution: wont fix
Dependencies: Superseder: Close 2to3 issues and list them here
View: 45544
Assigned To: Nosy List: benjamin.peterson, ccanepa, eric.araujo
Priority: normal Keywords: patch

Created on 2014-03-07 21:14 by ccanepa, last changed 2022-04-11 14:57 by admin. This issue is now closed.

File name Uploaded Description Edit
fix_import.diff ccanepa, 2014-03-07 21:14 diff with a proof of concept fix
Messages (3)
msg212899 - (view) Author: Claudio Canepa (ccanepa) Date: 2014-03-07 21:14
0. windows specific

i. In the pyglet library, written for py2 and officially running in 3 after the stock installation that does the 2to3 conversion

ii. Omitting files which are unimportant for the issue, the package dir looks as

(each package - subpackage has a proper

iii. In the pyglet repository checkout, near the begining of theres the block

    import Image
except ImportError:
    from PIL import Image

That PIL refers to the pillow package (fork of PIL, and yes it its the recommended import line in pillow's doc)

iv. after installing with
   cd working_copy
   py -3.3 install

the same block looks as

    import Image
except ImportError:
    from .PIL import Image

which is wrong, and precludes pyglet to import Pillow.

v. I tracked the problem to (CPython) LIB/lib2to3/fixes/

In  method FixImport.probably_a_local_import the heuristic is
"if 'import name' is seen, look if theres a sibling file with that name, and if exists assume it needs to be a relative import"

The problem is that the implementation uses os.path.exists to check sibling existence, but that has false positive cases due to Windows case-insensivity for filenames.

Module names are case-sensitive.

So, the import machinery would never match PIL to pil, but the code in will merrily match.

vi. To verify the issue I patched, deleted the old pyglet install under 3, reinstalled: Now the block is unmolested.
Attached the diff with the fixed code (diff obtained with the GNU C utils)

vii. This was seen in python 3.3.1 , on Windows xp sp3.
I see in the cpython repo the same issue will happen in the default branch (the offending lines in are unchanged, so I assume 3.4 will show the same defect)

viii. as a reference, the original issue in pyglet can be found at

ix. Anyone can suggest a workaround, a change in the problematic block in pyglet that would tell 2to3 to not change the block ?
msg213581 - (view) Author: Éric Araujo (eric.araujo) * (Python committer) Date: 2014-03-14 18:26
Hello, thanks for the report.  Is this the same issue as #19510?
msg213586 - (view) Author: Claudio Canepa (ccanepa) Date: 2014-03-14 19:31
No. #19510 is about 2 to 3 confused when the same import line has some modules that should be 'relativized' and others that not.

The present issue is about 2to3 incorrectly 'relativize' a module / package by forgetting that module names are case-sensitive but filenames are case-insensitive in windows.
Date User Action Args
2022-04-11 14:57:59adminsetgithub: 65066
2021-10-20 22:39:23iritkatrielsetstatus: open -> closed
superseder: Close 2to3 issues and list them here
resolution: wont fix
stage: resolved
2014-03-14 19:31:29ccanepasetmessages: + msg213586
2014-03-14 18:26:52eric.araujosetnosy: + eric.araujo
messages: + msg213581
2014-03-07 21:27:36ned.deilysetnosy: + benjamin.peterson
2014-03-07 21:14:30ccanepacreate