Re: [Zope-dev] How to override __getattr__ and not break acquisition
I perhaps should have clarified that I need to be able to specify the name of the attributes or methods at run time, so ComputedAttribute unfortunately won't do the trick as you have to define each attribute/method you require in the class definition. ie. I need something like : def __getattr__(self,attr): if name in self.methodlist: do something return Implicit.__class__.__getattr__(self,attr) where self.methodlist is a list of strings that may change per instance and/or at runtime, or itself could be calculated at the time of doing the __getattr__ (eg self.getMethodList()). Sounds like you could use ZPatterns. If you do implement your own __getattr__, you might need to check if the object you want to return implements __of__, and return object.__of__(self) (or something like that). -- Steve Alexander ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
Casey Duncan wrote: __getattr__ hooks are evil, only to be used as a last resort. Are you So I've found, and heard! It didn't stop me from tyring, and I still don't see why they should be so hard so work with, difficult perhaps, but I wouldn't have though you needed to pull the seemingly impossible to have them work (with zope at least)! creating some sort of transparent proxy object? What exactly are you trying to do? I'm not getting a big picture here. And why do you need See my last post (I posted it before I saw this one sorry), but basically I want a link/reference type functionality that hooks in before containment acquisition, and I think I've worked it out another way to do it as per that post. to call the inherited __getattr__ from Implicit? Doesn't raising an AttributeError take care of this? Yes it does, but it wasn't so simple in this case (This is where the 'evil' you mentioned earlier comes in). Part of my problem was the need to call another class method on self which in turn needs to access a method on self that comes from containment acquisition on self, which would call my overridden __getattr__ and have an exception rasied due to not doing containment acquisition. This exeption would then be caught in the code calling the first __getattr__ call, and not the second. Can python not handle exceptions properly with recursive function calls, or was this my bad analysis and/or just being generally confused? One other way that may work is to be able to set methods on the object as it comes out of the ZODB for use, as I need to be able to get methods from other objects in the ZODB, something to explore... Anyone have any pointers on this one perhaps? Yes, but that would change the attributes and cause the ZODB to save them on commit (unless you use volatile '_v_' attrs). This might not be a bad thing. I might be able to use _v_ attrs, otherwise the storing bit would be very bad unless the store method was also overriden and they were deleted on the way out. Thanks, JB. ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
There is no default or normal __getattr__. __getattr__ is defined only when you need abnormal ways of getting an attribute. Do you mean it only gets defined when standard (instance class based) searching methods fail? If I try a similar thing to this, I always end up getting the 'old' one being defined as just the 'raise' statement. Thats because ObjectManager doesn't have a __getattr__ . The good thing with Object Manager doesn't specifically, but Implicit does, you can see it if you print out its '__class__.__dict__'. this is that you don't have to bother about calling the normal __getattr__. You only need to implement __getattr__ if you want data that isn't attributes and has names that are only defined in runtime, to look like they are attributes. Exactly what I need! :-) Thankfully these methods that I need defined at runtime only come from one other object, so it appears I can override the __of__ method to work the magic for me in conjunction with containment acquisition. Thanks, JB. ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
From: John Barratt [EMAIL PROTECTED] Do you mean it only gets [called] when standard (instance class based) searching methods fail? Yes. At least, this is what the documentation sais, and it seems to be true as far as I can see. Object Manager doesn't specifically, but Implicit does, you can see it if you print out its '__class__.__dict__'. Ah, OK, I never did any really thorough research in that department. I have, in any case, gotten the same results as you, so in that case you probably need to call Implicits.__getattr__ directly. I haven't seen any negative effects of not doing this, though. I'm not well versed enough in how to write python stuff in c, so I don't understand it very well. Just well enough to not be able to find Implicits __getattr__. :-) Exactly what I need! :-) Thankfully these methods that I need defined at runtime only come from one other object, so it appears I can override the __of__ method to work the magic for me in conjunction with containment acquisition. Yup, much better way. __getattr__ is more for if you have a dictionary which data you want as attributes. ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
Erik A. Dahl wrote: Ok I need to override __getattr__ in one of my product classes. I'm sure this is killing acquisition yes but not sure about the persistence stuff (I think this is working). it will still work Is there a way to make this work? yes Here is what I'm doing: def __getattr__(self, name): if name == 'myattr': return self.myattr() if your return value knows about acquisition, you need to it by calling __of__: def __getattr__(self, name): if name == 'myattr': return self.myattr().__of__(self) I assume that somewhere in the Acquisition code there is a __getattr__ but I can't find it. it is implemented in C. -- Steve Alexander ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
If your __getattr__ fails to find what it wants, it should raise an AttributeError. This will give the ball back to the acquisition machinery. Thusly: def __getattr__(self, name): if name = 'foo': return self.foo() raise AttributeError, name hth, -Casey On Tue, 2002-06-04 at 22:28, Erik A. Dahl wrote: Ok I need to override __getattr__ in one of my product classes. I'm sure this is killing acquisition but not sure about the persistence stuff (I think this is working). Is there a way to make this work? Here is what I'm doing: def __getattr__(self, name): if name == 'myattr': return self.myattr() I assume that somewhere in the Acquisition code there is a __getattr__ but I can't find it. I tried calling Implicit.__getattr__ but its not there. If some one has an example that would be great. -EAD ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope ) ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
Re: [Zope-dev] How to override __getattr__ and not break acquisition
How about making __setattr__ work ? I keep having Acquisition tell me that it cannot find the Acquisition.Acquired properties. Nic On Wednesday 05 June 2002 09:21 am, Casey Duncan wrote: If your __getattr__ fails to find what it wants, it should raise an AttributeError. This will give the ball back to the acquisition machinery. Thusly: def __getattr__(self, name): if name = 'foo': return self.foo() raise AttributeError, name hth, -Casey On Tue, 2002-06-04 at 22:28, Erik A. Dahl wrote: Ok I need to override __getattr__ in one of my product classes. I'm sure this is killing acquisition but not sure about the persistence stuff (I think this is working). Is there a way to make this work? Here is what I'm doing: def __getattr__(self, name): if name == 'myattr': return self.myattr() I assume that somewhere in the Acquisition code there is a __getattr__ but I can't find it. I tried calling Implicit.__getattr__ but its not there. If some one has an example that would be great. -EAD ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
[Zope-dev] How to override __getattr__ and not break acquisition
Ok I need to override __getattr__ in one of my product classes. I'm sure this is killing acquisition but not sure about the persistence stuff (I think this is working). Is there a way to make this work? Here is what I'm doing: def __getattr__(self, name): if name == 'myattr': return self.myattr() I assume that somewhere in the Acquisition code there is a __getattr__ but I can't find it. I tried calling Implicit.__getattr__ but its not there. If some one has an example that would be great. -EAD ___ Zope-Dev maillist - [EMAIL PROTECTED] http://lists.zope.org/mailman/listinfo/zope-dev ** No cross posts or HTML encoding! ** (Related lists - http://lists.zope.org/mailman/listinfo/zope-announce http://lists.zope.org/mailman/listinfo/zope )
