__getattr__, __setattr__ and pickle

[mwojc]

Hi!
My class with implemented __getattr__ and __setattr__ methods cannot be
pickled because of the Error:

=============== =============== =============== =============== ==========
ERROR: testPickle (__main__.TestD effnet2WithBias es)
----------------------------------------------------------------------
Traceback (most recent call last):
File "deffnet.py ", line 246, in testPickle
cPickle.dump(se lf.denet, file)
TypeError: 'NoneType' object is not callable

----------------------------------------------------------------------

Is there an obvious reason i don't know, which prevents pickling with those
methods (if i comment them out the pickling test passes)?

I'm using Python 2.4.4 on Gentoo Linux. The mentioned methods goes as
follows:

def __setattr__(sel f, name, value):
if name == 'weights':
j = 0
for net in self.nets:
w1 = self.wmarks[j]
w2 = self.wmarks[j+1]
net.weights = value[w1:w2]
j += 1
else:
self.__dict__[name] = value

def __getattr__(sel f, name):
if name == 'weights':
j = 0
for net in self.nets:
w1 = self.wmarks[j]
w2 = self.wmarks[j+1]
self._weights[w1:w2] = net.weights
j += 1
return self._weights

Greetings,
--
Marek

[mwojc]

Re: __getattr__, __setattr__ and pickle

Bruno Desthuilliers wrote:

mwojc a écrit :

>Hi!
>My class with implemented __getattr__ and __setattr__ methods cannot be
>pickled because of the Error:
>>
>============== =============== =============== =============== ===========
>ERROR: testPickle (__main__.TestD effnet2WithBias es)
>----------------------------------------------------------------------
>Traceback (most recent call last):
> File "deffnet.py ", line 246, in testPickle
> cPickle.dump(se lf.denet, file)
>TypeError: 'NoneType' object is not callable
>>
>----------------------------------------------------------------------
>>
>Is there an obvious reason i don't know, which prevents pickling with
>those methods (if i comment them out the pickling test passes)?
>>
>I'm using Python 2.4.4 on Gentoo Linux. The mentioned methods goes as
>follows:
>>
> def __setattr__(sel f, name, value):
> if name == 'weights':
> j = 0
> for net in self.nets:
> w1 = self.wmarks[j]
> w2 = self.wmarks[j+1]
> net.weights = value[w1:w2]
> j += 1
> else:
> self.__dict__[name] = value
>>
> def __getattr__(sel f, name):
> if name == 'weights':
> j = 0
> for net in self.nets:
> w1 = self.wmarks[j]
> w2 = self.wmarks[j+1]
> self._weights[w1:w2] = net.weights
> j += 1
> return self._weights

>
__getattr__ should raise an AttributeError when name != 'weight' instead
of (implicitely) returning None. pickle looks for a couple special
method in your object[1], and it looks like it doesn't bother to check
if what it found was really callable.

Yes, raising AttributeError helped. Thanks!

>
FWIW, you'd be better using a property instead of __getattr__ /
__setattr__ if possible.

You're probably right again, in this case it's better to use property.

And while we're at it, you dont need to
manually take care of your index in the for loop - you can use
enumerate(itera ble) instead:
>
for j, net in enumerate(self. nets):
w1 = self.wmarks[j]
w2 = self.wmarks[j+1]
self._weights[w1:w2] = net.weights
return self._weights
>

Sometimes i use manual handling of index because i'm convinced that
enumeration is a bit slower than this. But i'm not really sure about it...

Thanks again.

Greetings,
--
Marek

[Michele Simionato]

Re: __getattr__, __setattr__ and pickle

On Aug 12, 7:28 pm, mwojc <mw...@NOSPAMp. lodz.plwrote:

Hi!
My class with implemented __getattr__ and __setattr__ methods cannot be
pickled because of the Error:

Another option is to define __getstate__ on your class:

def __getstate__(se lf): return vars(self)


M.S.