[ZODB-Dev] Re: getting the object ID (_p_oid attribute)

[Florent Guillaume]

On 26 Jun 2006, at 21:11, Robert Gravina wrote:
> On 2006/06/27, at 3:49, Benji York wrote:
>> Robert Gravina wrote:
>>> I just tried loading a persisted  object interactively and  
>>> noticed that although the _p_oid doesn't  print out as anything  
>>> (and hence I always thought it was empty in my  debugging  
>>> prints), it isn't actually None! Can anyone explain this?  (here  
>>> "p" is my persisted object)
>>>  >>> p._p_oid
>>> '\x00\x00\x00\x00\x00\x00\x00\x08'
>>>  >>> print p._p_oid
>>>  >>> p._p_oid is None
>>> False
>>
>> What would you expect to see if you printed out seven null  
>> characters and a backspace?
>
> Hahaha - that's a good point! I was expecting IDs to look, well,  
> something like "asdf23asdf". Well, anyway thankyou! I seemed to  
> have solved this problem. I was able to write a __eq__ function  
> like this:
>
>     def __eq__(self, other):
>         if isinstance(other, <name of my class>):
>             if hasattr(other,"_p_oid") and other._p_oid != None and  
> (other._p_oid == self._p_oid):
>                 return True
>             else:
>                 return False
>
> and now can compare objects for equality after the (Twisted) client  
> edits them and sends them back.

You can shorten that to
def __eq__(self, other):
     return aq_base(self) is aq_base(other)

And you can ditch the aq_base if you don't use acquisition-based  
classes.

Florent

-- 
Florent Guillaume, Nuxeo (Paris, France)   Director of R&D
+33 1 40 33 71 59   http://nuxeo.com   fg at nuxeo.com