weird pickle behavior in Python 3.1.2 + Eclipse 3.5.2

[Fabio Zadrozny]

On Mon, Jun 7, 2010 at 6:30 AM, Peter Otten <__peter__ at web.de> wrote:
> kirby.urner at gmail.com wrote:
>
>> On Jun 4, 9:47 am, Peter Otten <__pete... at web.de> wrote:
>>
>>> I can provoke the error in "naked" Python 3 by changing the
>>> Example.__module__ attribute:
>>>
>>> Python 3.1.1+ (r311:74480, Nov  2 2009, 15:45:00)
>>> [GCC 4.4.1] on linux2
>>> Type "help", "copyright", "credits" or "license" for more information.
>>
>>> >>> import pickle
>>> >>> class Example:
>>>
>>> ...     pass
>>> ...
>>> >>> pickle.dumps(Example())
>>>
>>> b'\x80\x03c__main__\nExample\nq\x00)\x81q\x01}q\x02b.'
>>
>>> >>> Example.__module__ = "builtins"
>>> >>> pickle.dumps(Example())
>>>
>>> Traceback (most recent call last):
>>> File "<stdin>", line 1, in <module>
>>> File "/usr/lib/python3.1/pickle.py", line 1358, in dumps
>>> Pickler(f, protocol, fix_imports=fix_imports).dump(obj)
>>> _pickle.PicklingError: Can't pickle <class 'Example'>: attribute lookup
>>> builtins.Example failed
>>>
>>> What's the value of __module__ when you run your code in Eclipse?
>>>
>>> Peter
>>
>> Thank you for replying.
>>
>> Here's from Eclipse console:
>>
>>>>> Example.__module__
>> 'builtins'
>>
>>>>> __name__
>> 'builtins'
>>
>> Duplicating your result in naked Python:
>>
>> Python 3.1.2 (r312:79149, Mar 21 2010, 00:41:52) [MSC v.1500 32 bit
>> (Intel)] on win32
>> Type "copyright", "credits" or "license()" for more information.
>>>>> class Example:
>> pass
>>
>>>>> import pickle
>>>>> Example.__module__
>> '__main__'
>>>>> f = open('testpickle.pkl','wb')
>>>>> obj = Example()
>>>>> obj
>> <__main__.Example object at 0x02A26690>
>>>>> pickle.dump(obj, f)
>>
>>>>> Example.__module__ = 'builtins'
>>>>> obj2 = Example()
>>
>>>>> pickle.dump(obj2, f)
>> Traceback (most recent call last):
>>   File "<pyshell#12>", line 1, in <module>
>>     pickle.dump(obj2, f)
>>   File "C:\Python31\lib\pickle.py", line 1354, in dump
>>     Pickler(file, protocol, fix_imports=fix_imports).dump(obj)
>> _pickle.PicklingError: Can't pickle <class 'Example'>: attribute
>> lookup builtins.Example failed
>>
>> So what if I'm in an Eclipse pydev console and
>> change the Example.__module__ to '__main__'....
>>
>>>>> import sys; print('%s %s' % (sys.executable or sys.platform,
>>>>> sys.version))
>> C:\Python31\python.exe 3.1.2 (r312:79149, Mar 21 2010, 00:41:52) [MSC
>> v.1500 32 bit (Intel)]
>>>>> import pickle
>>>>> class Example:
>> ...     pass
>> ...
>>>>> Example.__module__
>> 'builtins'
>>>>> Example.__module__ = '__main__'
>>>>> obj = Example()
>>>>> obj
>> <__main__.Example object at 0x029E8FD0>
>>>>> f = open('testpickle.pkl','wb')
>>>>> pickle.dump(obj, f)
>> Traceback (most recent call last):
>>   File "<console>", line 1, in <module>
>>   File "C:\Python31\lib\pickle.py", line 1354, in dump
>>     Pickler(file, protocol, fix_imports=fix_imports).dump(obj)
>> _pickle.PicklingError: Can't pickle <class '__main__.Example'>:
>> attribute lookup __main__.Example failed
>>>>>
>>
>> Dang.
>>
>> Any insights?
>
> Sorry, no. Consider a bug report to the pydev project.
>


I've taken a look at the pydev code and the issue seems to be in
python itself. See: http://bugs.python.org/issue8943

Cheers,

Fabio