How to stop attributes from being pickled in Python [duplicate]

Question

I am using gnosis.xml.pickle to convert an object of my own class to xml. The object is initialized so that:

self.logger = MyLogger() 

But when I do dump the object to a string I get an exception stating that the pickler encountered an unpickleable type (thread.lock).

Is there a way to 'tag' the logger attribute so that pickler will know not to try and pickle that attribute?

Answer 1

You can define two methods, __getstate__ and __setstate__, to your class to override the default pickling behavior.

http://docs.python.org/library/pickle.html#object.__getstate__

__getstate__ should return a dict of attributes that you want to pickle.

def __getstate__(self):     d = dict(self.__dict__)     del d['logger']     return d 

__setstate__ should setup your object with the provided dict.

def __setstate__(self, d):     self.__dict__.update(d) # I *think* this is a safe way to do it 

Note that __init__ won't be called when unpickling so you'll have to create your logger in __setstate__

Answer 2

This might be a better solution since it will allow an object created via copy.deepcopy to still have a self.logger:

def __getstate__(self):     d = self.__dict__.copy()     if 'logger' in d:         d['logger'] = d['logger'].name     return d  def __setstate__(self, d):     if 'logger' in d:         d['logger'] = logging.getLogger(d['logger'])     self.__dict__.update(d)