[issue13591] import_module potentially imports a module twice

2011-12-14 Thread Brett Cannon 

Brett Cannon br...@python.org added the comment:

Patch looks good to me.

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stage: patch review - commit review

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[issue13591] import_module potentially imports a module twice

2011-12-14 Thread Roundup Robot 

Roundup Robot devn...@psf.upfronthosting.co.za added the comment:

New changeset d2504d30f259 by Meador Inge in branch '3.2':
Issue #13591: import_module potentially imports a module twice.
http://hg.python.org/cpython/rev/d2504d30f259

New changeset e8fb61a0a2d7 by Meador Inge in branch 'default':
Issue #13591: import_module potentially imports a module twice.
http://hg.python.org/cpython/rev/e8fb61a0a2d7

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[issue13591] import_module potentially imports a module twice

2011-12-14 Thread Meador Inge 

Meador Inge mead...@gmail.com added the comment:

Thanks for the review Brett.  Fix committed.

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[issue13591] import_module potentially imports a module twice

2011-12-14 Thread Roundup Robot 

Roundup Robot devn...@psf.upfronthosting.co.za added the comment:

New changeset 541f215a31f7 by Meador Inge in branch '3.2':
Issue #13591: Moving the NEWS line to the right release.
http://hg.python.org/cpython/rev/541f215a31f7

New changeset 92e94fd303d4 by Meador Inge in branch 'default':
Issue #13591: Moving the NEWS line to the right release.
http://hg.python.org/cpython/rev/92e94fd303d4

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[issue13591] import_module potentially imports a module twice

2011-12-13 Thread Meador Inge 

Meador Inge mead...@gmail.com added the comment:

I can reproduce this on tip.  What happens is that 
'importlib.import_module(my_lib.bar)' is effectively computed as:

   import my_lib
   import bar

by '_bootstrap._gcd_import'.  When '_gcd_import' goes to do the import
of 'bar' it does *not* check to see if 'bar' has already been imported
by the parent import.

Here is a patch *without* tests that fixes this.  I will add the tests
next.

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stage:  - patch review
Added file: http://bugs.python.org/file23943/issue13591.patch

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[issue13591] import_module potentially imports a module twice

2011-12-13 Thread Antoine Pitrou 

Changes by Antoine Pitrou pit...@free.fr:


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versions: +Python 3.3

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[issue13591] import_module potentially imports a module twice

2011-12-13 Thread Ryan Twitchell 

Ryan Twitchell metatheo...@gmail.com added the comment:

Confirmed that this patch fixes the behavior shown in my original example, with 
3.2.

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[issue13591] import_module potentially imports a module twice

2011-12-13 Thread Meador Inge 

Meador Inge mead...@gmail.com added the comment:

Updated patch with tests.

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Added file: http://bugs.python.org/file23951/issue13591-2.patch

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[issue13591] import_module potentially imports a module twice

2011-12-12 Thread Ryan Twitchell 

New submission from Ryan Twitchell metatheo...@gmail.com:

Use of importlib's import_module function with modules belonging to a library
can cause some modules to be imported twice, if such a module is referenced
from sibling modules, and from __init__ in the package.  I suspect this is a
bug, or at best a nuance of packages that is quite subtle.

Easier to show with an example.  Below, the module my_lib.bar will be imported
twice.  Given the following file structure:

./scratch.py
./my_lib/__init__.py
./my_lib/foo.py
./my_lib/bar.py

And the following file contents:

./scratch.py:

import importlib
importlib.import_module('my_lib.bar')
importlib.import_module('my_lib.foo')


./my_lib/__init__.py:

import my_lib.bar

# Or alternately
#from . import bar


./my_lib/foo.py:

from . import bar

print('In foo, id(bar.baz): %s' % id(bar.baz))


./my_lib/bar.py:

def baz():
pass

print('In bar, id(bar.baz): %s' % id(baz))


Running scratch.py results in my_lib.bar being imported twice:
$ echo $PYTHONPATH
.
$ python --version
Python 3.2.2
$ python ./scratch.py
In bar, id(bar.baz): 21328632
In bar, id(bar.baz): 21352240
In foo, id(bar.baz): 21352240


Replacing the calls to import_module with use of the import statement, or
__import__, or simply rearranging the order of the two calls all result in the
module my_lib.bar to be imported only once.  As does eliminating the import
statement in my_lib.__init__.

This may be a misunderstanding on my part regarding the intended use of
packages, but this behavior was quite unexpected, and rather difficult to track
down in real code.

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components: Library (Lib)
messages: 149358
nosy: Ryan.Twitchell
priority: normal
severity: normal
status: open
title: import_module potentially imports a module twice
type: behavior
versions: Python 3.2

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[issue13591] import_module potentially imports a module twice

2011-12-12 Thread Ezio Melotti 

Changes by Ezio Melotti ezio.melo...@gmail.com:


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[issue13591] import_module potentially imports a module twice

2011-12-12 Thread Meador Inge 

Changes by Meador Inge mead...@gmail.com:


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[issue13591] import_module potentially imports a module twice

2011-12-12 Thread Nick Coghlan 

Nick Coghlan ncogh...@gmail.com added the comment:

At first glance, I thought this might be just the circular import problem 
(#992389) appearing in a different guise. However, if that was the case, 
switching to an import statement or __import__ shouldn't have made any 
difference.

What do you see if you put an import my_lib.bar *between* the two importlib 
calls?

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