Re: PyCXX question on __module__ attribute

[Barry S. <ba...@ba...>]

> On 27 Apr 2016, at 20:24, kishor sharma <kis...@gm...> wrote:
> 
> Hi CXX Users,
> 
> I am using PyCXX to write extension classes. I am trying to pickle the extension object using cPickle. cPickle break as __module__ attribute is not on the objects
> e.g. 
> 
> In [1]: import example
> range object created 0x196b290
> range object destroyed 0x196b290
> 
> In [2]: example.range.__name__
> Out[2]: 'range'
> 
> In [3]: example.range.__doc__
> Out[3]: 'range(start,stop,stride)'
> 
> In [4]: example.range.__module__
> 
> In [5]: example.range.__module__ is None
> Out[5]: True
> 
> I tried debugging the code it seems to be passing correct module name to Py_InitModule4 function but it is not reflected in the python. 
> 
> Any help/pointers on how to fix? 

Its been a long time since I used pickle. Personally I would avoid pickle because of the security and robustness issues.

Anyway. It looks like if you want to pickle an extension object you have to implement the
__reduce__ and/or __reduce_ex__ methods. You would have to see what pickle does with the tuple returned by __reduce__ to recreate the objects. You can also register functions to assist pickle.

Given that the reason a C++ extension module is created is to wrap around complex resources I wonder if
its reasonable to attempt to pickle a C++ object.

Barry


> 
> Thanks,
> Kishor Sharma
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