[Numpy-discussion] Possible to pickle new state in NDArray subclasses?

[Stuart Reynolds]

Works great! Thank you.

On Wed, Dec 14, 2016 at 11:51 AM, Nathan Goldbaum <nathan12343 at gmail.com>
wrote:

> I'm able to do this in my ndarrary subclass using __reduce__ and
> __setstate__:
>
> https://bitbucket.org/yt_analysis/yt/src/yt/yt/units/
> yt_array.py#yt_array.py-1250
>
> Here it's being used to save the unit information into the pickle for a
> unit-aware ndarray subclass.
>
> On Wed, Dec 14, 2016 at 1:45 PM, Stuart Reynolds <
> stuart at stuartreynolds.net> wrote:
>
>> I'm trying to subclass an NDArray as shown here:
>>    https://docs.scipy.org/doc/numpy/user/basics.subclassing.html
>>
>> My problem is that when I save the new class' state with pickle, the new
>> attributes are lost. I don't seem to be able to override __getstate__ or
>> __setstate__ to achieve this?
>>
>> Is it possible to allow new state to serialized when overriding an
>> NDArray?
>>
>> In my example below, __setstate__ gets called by pickle but not
>> __getstate__.
>> In the final line, a RealisticInfoArray has been deserialized, but it has
>> no .info attribute.
>>
>> ----
>>
>> import cPickle as pickle
>> import numpy as np
>>
>> class RealisticInfoArray(np.ndarray):
>>     def __new__(cls, arr, info):
>>         obj = np.asarray(arr).view(cls)
>>         obj.info = info
>>         return obj
>>
>>     def __array_finalize__(self, obj):
>>         if obj is None: return
>>         self.info = getattr(obj,"info",None)
>>
>>     def __setstate__(self, *args):
>>         print "SET"
>>         return np.ndarray.__setstate__(self,*args)
>>
>>     def __getstate__(self):
>>         print "GET"
>>         assert False, "EXPLODE"
>>         return np.ndarray.__getstate__(self)
>>
>> arr = np.zeros((2,3), int)
>> arr = RealisticInfoArray(arr, "blarg")
>> print arr.info
>> arr2 = pickle.loads(pickle.dumps(arr))
>> print arr2.info  # no .info attribute!
>>
>>
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>>
>
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