cPickle and __getattr__

Paul Morrow pm_mon at yahoo.com
Mon Aug 30 02:33:53 CEST 2004


Chris Curvey wrote:

> Hi all,
> 
> I have this program
> 
> class Company:
>    def __init__(self, revenues, costs):
>       self.revenues = revenues
>       self.costs = costs
> 
>    def __getattr__(self, name):
>        if name == 'profits':
>            return self.revenues - self.costs
> 
> c = Company(100, 75)
> print c.revenues
> print c.costs
> print c.profits
> 
> import cPickle
> print cPickle.dumps(c)
> 
> Everything works fine up until the last line.  If I remove the 
> __getattr__ function, then everything works (except "print c.profits"). 
>  What is the cPickle class trying to get to that is causing my 
> __getattr__ function to be called?
> 
> -Chris
> 

When you use __getattr__, you should always raise an attribute error for 
names that you don't handle.

     def __getattr__(self, name):
         if name == 'profits':
             return self.revenues - self.costs
         else:
             raise AttributeError, name

Paul




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