[Python-Dev] On breaking modules into packages Was: [issue10199] Move Demo/turtle under Lib/

[Michael Foord]

On 03/11/2010 14:26, Michael Foord wrote:
> On 03/11/2010 14:17, Antoine Pitrou wrote:
>> Le mercredi 03 novembre 2010 à 14:16 +0000, Michael Foord a écrit :
>>> On 03/11/2010 14:05, Nick Coghlan wrote:
>>>> On Wed, Nov 3, 2010 at 9:32 AM, Raymond Hettinger
>>>> <raymond.hettinger at gmail.com>   wrote:
>>>>> Sounds like a decision to split a module into a package is a big 
>>>>> commitment.  Each of the individual file names becomes a permanent 
>>>>> part of the API.  Even future additional splits are precluded 
>>>>> because it might break someones dotted import (i.e. not a single 
>>>>> function can be moved between those files -- once in 
>>>>> unittest.utils, alway in unittest.utils).
>>>> Can Python 2.7 pickles containing unittest classes be unpickled using
>>>> 2.6 or earlier? Even if nobody uses the new names for imports, I
>>>> believe they implicitly end up included in any pickles involving
>>>> affected classes (I seem to recall we've been bitten by that before
>>>> when moving things around).
>>> Yes, since unittest.TestCase is still available (as are all the names).
>>> I believe so anyway...
>> unittest.TestCase is not really pickleable. There were
>> test_multiprocessing issues because of that (see recent SVN checkins).
>
> Interesting. We made some fixes before 2.7 to ensure they were 
> copyable, but we fixed this in the copy module. TestCase instances now 
> store some method objects in a dictionary which may make them 
> unpickleable, so that could be a new problem. I'll test with 2.6 and 
> 2.7 to see.
>
> An easy fix would be to store the method names rather than the method 
> objects themself (if this is indeed the cause of the problem). This is 
> what unittest2 does so that it works with earlier versions of Python 
> that don't have the fix we put in copy.
>
Yep, looks like 2.7 introduced a bug making it impossible to pickle 
TestCase instances. I think it will be easy to fix, I'll create a 
specific issue:

$python
Python 2.6.5 (r265:79359, Mar 24 2010, 01:32:55)
[GCC 4.0.1 (Apple Inc. build 5493)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
 >>> from unittest import TestCase
 >>> from pickle import dumps
 >>> t = TestCase('assert_')
 >>> dumps(t)
"ccopy_reg\n_reconstructor\np0\n(cunittest\nTestCase\np1\nc__builtin__\nobject\np2\nNtp3\nRp4\n(dp5\nS'_testMethodDoc'\np6\nS'Fail 
the test unless the expression is 
true.'\np7\nsS'_testMethodName'\np8\nS'assert_'\np9\nsb."
 >>>
bigmac:beta.python.org michael$ python2.7
ActivePython 2.7.0.1 (ActiveState Software Inc.) based on
Python 2.7 (r27:82500, Jul  4 2010, 13:58:56)
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
 >>> from unittest import TestCase
 >>> from pickle import dumps
 >>> t = TestCase('assert_')
 >>> dumps(t)
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File 
"/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", 
line 1374, in dumps
     Pickler(file, protocol).dump(obj)
...
   File 
"/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/pickle.py", 
line 306, in save
     rv = reduce(self.proto)
   File 
"/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/copy_reg.py", 
line 70, in _reduce_ex
     raise TypeError, "can't pickle %s objects" % base.__name__
TypeError: can't pickle instancemethod objects

All the best,

Michael

> Michael
>
>> Regards
>>
>> Antoine.
>>
>>
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>


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