May 2000 - Zope - Zope lists

RE: [Zope] Subclassing from Custom Python Classes
by Chris McDonough 25 May '00

25 May '00

This is a good question that I'm not sure of the completely technically correct answer to. But here's my best shot. Part of what composes a "Zope object" is that the object inherits characteristics from the "Persistence.Persistent" class. This base class overrides Python's normal __setattr__ and __getattr__ instance methods. When a persistent object is queried for a subobject (e.g. its __getattr__ is called), it does some magic to pull that subobject out of persistent storage. Likewise, when you attach an attribute to an object (e.g. its __setattr__ is called), this base class does its thing and when a transaction is committed, the object is written out to the ZODB. Because mutable objects have methods that do an end-run around __setattr__ (such as list.append, dict.__setitem__, etc.), Zope won't know that the object has changed because setattr never gets called. However, when you do the persistence shuffle (ala m=self.map; m['foo']=bar; self.map=m), __setattr__ does get called on the parent object, and Zope therefore knows the object has been changed. Others may elaborate or correct, I'm certain. > -----Original Message----- > From: Pete Kazmier [mailto:pete@kazmier.com] > Sent: Wednesday, May 24, 2000 8:32 PM > To: zope(a)zope.org > Cc: chrism(a)digicool.com > Subject: Re: [Zope] Subclassing from Custom Python Classes > > > Thank you for the useful information!! > > I do have one more question regarding your persistence comments. How > does using a temporary name notify the Zope persistence machinery that > self.map has changed? Doesn't 'self.map=m' do nothing in Python if > one already did a 'm=self.map'? In the end, aren't they referencing > the exact same object? Hows does Zope know its different? > > Thanks again, > Pete >

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Re: [Zope] seq-items and nested dtml-ins
by Tres Seaver 25 May '00

25 May '00

Aaron Payne <aaron(a)aaronpayne.com> > > How do you differentiate between the seq-items of nested dtml-ins? > > I tried the following code: > > <dtml-in "instances.objectValues(['Coupon ZClass'])"> > > <dtml-in SearchCategory> > <dtml-if "_['sequence-item']=='Auto' "> > <dtml-call "resultsList.append(_['sequence-item'])"> > </dtml-if> > </dtml-in end SearchCategory> > > </dtml-in end instances> > > Where: > instances is a folder containing the coupon instances > Coupon ZClass is the meta type of the zclass > SearchCategory is a list from a form > resultsList is a list containing instances of Coupon ZClass matching the > search criteria > Auto is a property of Coupon ZClass > > When I try to run a search an error page pops up saying "strings aren't > allowed as input in the in tag." > > The property Category of the zclass is the type lines. "Auto' is one of > the values in Category. > In <dtml-if "_['sequence-item']=='Auto' "> I am comparing the current > element of SearchCategory to one of the values in Category. Your code to deal with SearchCategory looks OK to my. Try a couple of things: * Try dumping the REQUEST variable (e.g., '<dtml-var REQUEST>' in your form handler) and make sure that the SearchCategory is actally a list. * Make sure you leverage the ZPublisher marshalling machinery to force SearchCategory to be converted to a list, even if the user selects only one item, e.g.:: <select name="SearchCategory:list" multiple> ^^^^^ on your form. > In <dtml-call resultsList...> I want to append the instance and not > SearchCategory list. For the moment, you need to alias the "outer" sequence item, because the "inner" one hides it (by that name). So, in your case:: <dtml-in "instances.objectValues(['Coupon ZClass'])"> <dtml-let coupon=sequence-item>  <dtml-in SearchCategory> <dtml-if "_['sequence-item']=='Auto' "> <dtml-call "resultsList.append(coupon)"> ^^^^^^ </dtml-if> </dtml-in end SearchCategory> </dtml-let> </dtml-in end instances> Real Soon Now, you will be able to declare the alias for the sequence variable within the <dtml-in> tag itself, which would solve your problem nicely. For the details, see: http://www.zope.org/Members/4am/DTMLWiki/NamedDTMLInLoop Hope this helps! Tres. -- =========================================================== Tres Seaver tseaver(a)digicool.com Digital Creations "Zope Dealers" http://www.zope.org

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RE: [Zope] Subclassing from Custom Python Classes
by Chris McDonough 25 May '00

25 May '00

> >> You should also note that your subclass must obey the ZODB > >> persistence rules, which basically state that mutable sub-objects > >> should be treated immutably. For example, > >> > >> self.bird='parrot' # OK > >> self.map['bird']='parrot' # NOT OK, will not trigger persistence > >> machinery > >> m=self.map > >> m['bird']='parrot' > >> self.map=m # OK, treats a mutable object immutably > > What are these "persistence rules" and how come the second example is > ok? I thought in Python, when you assign "m = self.map" that m is > simply pointing to the same object as self.map and that any changes to > m affect self.map too? Does the "self.map = m" have any effect? > Don't they point to the same object? It's a long story. :-) Attributes of Zope objects need to play by some ground rules to be persistent. The description in the docs is sort of a half truth. It works as described, but you can also do something like: self.map['bird'] = 'parrot' self._p_changed = 1 to trigger the persistence machinery. The "m=self.map..." stuff in the example does the same thing. In either case you're bringing it to Zope's attention that it needs to at some point re-write the object referred to by "self" out to the ZODB. By doing the jiggery up there where you use "m" as a temp object, operate on it, and then reassign "self.map" to "m" in order to let Zope know you've really changed the object and that you really want to write a new copy of it out to the ZODB when it's convenient for it to do so. the _p_changed flag applies to any Zope object, and just needs to be set true at some point during the method to let the persistence machinery know that the object has changed state. In english the phrase "mutable sub-objects should be treated immutably" means that attributes of the Zope object you're mucking with that can be reassigned "in-place" (things you can append to like a list, or add items to like a dictionary) should be treated as though they can't be. So when saying (where 'self' is a Zope object): self.mylist.append("foo") This should be given special treatment, either by saying: self.mylist.append("foo") self._p_changed = 1 or mytmp = self.mylist mytmp.append("foo") self.mylist = mytmp > > I ask because I've already built my first product based on a custom > python class I wrote (its a router object that has methods to query > various snmp oids) based on a ZClass and I want to make sure that I am > not doing anything wrong. > In addition to the methods that query the oids, I store the results in > an instance variable of my Python class so I can cache the information > for a specified amount of time. Is this safe to do? Can I store > these values in my Python instance (self.xxxx), not a ZClass property? Sure, just make sure you abide by the stuff above. > Also, What happens if multiple people activate my query method, do I > need to worry about them stomping over each other as the method writes > the results to the instance variables? Is there any record locking of > objects? The ZODB will flag a ConflictError and will cause the second attempter to retry. This is pretty normal, and your data won't get munged. Look out, however, if you're really concerned, about "hot spots" that can effect performance. > Lastly, since I couldn't really find any pointers regarding a builtin > Zope scheduler that is bug free, I need to write a small python script > that I can place in a cron job to run every ten minutes to call the > query methods of these objects so they update their cache instances. > Is there a link on how to get a regular Python script access to the > ZODB? Yes... sort of. Try looking for a HowTo named "The Debugger is Your Friend" by Michel Pelletier. That shows you how to use the Zope module from inside python. It's simpler than you might expect. Here's an example (make sure you shut down your Zope before you try this or it won't work): [chrism@opar chrism]$ cd Zope2.1.6/lib/python [chrism@opar chrism]$ python >>> import Zope >>> app = Zope.app() >>> app <Application instance at 8455220> >>> dir(app) ['Control_Panel', '__allow_groups__'........] Play around inside Python, call methods on things, etc. This is a great way to learn more about Zope.

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2.1.4 to 2.1.6 nightmare
by Felipe Alvarez Harnecker 24 May '00

24 May '00

Hi Zopistas, after upgrading Zope (in a debian/Linux system) from 2.1.4 to 2.1.6 the acquisition rules seems to be broken. As an example supose we have this tree structure ---|- aviso |- foo |- bar |- X_sql (sql method) X_sql is a sql method with to parameters: objeto, aviso here is the template: INSERT INTO linea_publicacion (publicacion,aviso) VALUES (&dtml-objeto;,&dtml-aviso;) when zope renders this template to execute the sql, it renders INSERT INTO linea_publicacion (publicacion,aviso) VALUES (3,<Folder instance at 8580aa0>) so it replaces aviso with the folder instance aviso. Apart of discarding the explicit parameter "aviso", the aviso folder is not parent of bar so it shoudn't acquire it. So, who can explain me this?? is that a bug in Zope 2.1.6 ?? Zope 2.1.4 works fine. -- ______________________________________________________ Felipe Alvarez Harnecker. QlSoftware. Tel. 09.874.60.17 e-mail: felipe.alvarez(a)qlsoft.cl Potenciado por Ql/Linux http://www.qlsoft.cl/ ______________________________________________________

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Site search
by Nolan Darilek 24 May '00

24 May '00

I followed the helpful instructions in the Z Catalog tutorial concerning adding searching to my site, and it works, though not in the way that I'd like. I've added the raw field to the list of searched indices, and chosen to only index DTML documents. Yet, all of my searches seem to be case sensitive, and they all seem to be 'and' searches. I'm not particularly interested in supporting boolean keywords, but since my site isn't that large, it might make more sense to treat searches as 'or' searches by default. How difficult is it to implement case insensitive searches in this manner? Also, I've noticed that DTML documents don't appear to automatically add themselves to the Z catalog. My understanding is that all Z catalog-aware classes automatically notify the catalog when they are created; are DTML documents and methods not catalog-aware? Thanks.

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ZOPE ITALIAN Mailing List
by Marco Mariani 24 May '00

24 May '00

Sorry for bothering you. This is a one-time spam. A dozen people are being mailed in the back (blind carbon copy :-) I'd like to know if there's a need for an italian Zope list. Altough I'm OK reading or writing english, such a list could free some CPU cicles from my brain that I can devote to the Zen Of Zope or helping newbies. If somebody is interested, or can host the list, please reply privately. Thank you.

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Re: [Zope] The agony of the ZOPE Documentation
by Jerry Spicklemire 24 May '00

24 May '00

Jason Cunliffe wrote: >Perhaps you have a better crazier idea..I hope so:-) Maybe. I too have had problems with the ZDP stuff, but not specifically those mentioned by others in this thread. When I try to use the ZDP I am impressed by the effort and sheer volume of material, but unfortunately it seems to be mostly supported by non-native English speakers. The result is that I am often uncertain that I clearly understand what the author intended. That leaves me in a state that is nearly worse that where I began, potentially more knowledgable, but certainly more confused. Now, for that crazy solution. If the ZDP were in some Wiki-ish form that could be edited by readers ("Edit This Page", a la Frontier?), a new version of a page could be created to fix the most obvious misexpressions. The author might then be able to review the updates, and either approve the fixes, or clarify cases where a misfix has resulted from a misinterpretation, which itself is a verifiable indication that the original text was somewhat obscure. After a few passes through this process, the ZDP might be dressed up and ready to go to press! In a case like the proposal above, anyone willing to do some copyediting would be free to edit a paragraph at a sitting, if that's the all the time available, or a page, or a chapter. Whatever works. I know I have been reluctant to commit to any extensive participation simply because my time is very limited. Still, as tight as the schedule is, it isn't quite in the negative microseconds yet, so a graph per shift is better than nothing! With this in mind see the very recent post: http://lists.zope.org/pipermail/zope-dev/2000-May/005021.html This is a way to manage Zope Objects, stuff that usually lives in ZODB, using CVS. This can provide versioning, checkout, checkin, etc. It could be used as a way to let ZDP Authors know what's changed, at a very granualr level, to keep from having to wade through the page looking for somthing that isn't precisely as it was last time they saw it. ZDP is itself a Zope site, so this could be just the ticket. How can such a critter be set up? Thanks for considering a crazier idea, Jerry S.

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Re: [Zope] Re: [ZDP] Re: [Zope] The agony of the ZOPE Documentation
by Alan Shutko 24 May '00

24 May '00

Maik Roeder <roeder(a)berg.net> writes: > Do think that the basic idea of offering different portals for > different communities (Beginners, Developers and so on) is a bad > idea ? What do you think about the organisation in Subjects/Topics ? Well, as a brand-spanking new user (or user wannabe, if I can get the tutorial to run), I think that offering portals at all is a bad thing. I want information, not hoops to jump through to get information. Part of this is that I don't really like portals much in general, but a large part of it is that when I have problems, I go looking for information to solve those problems, and I don't want to have to guess where something would be filed (kind of hard when you don't know much). The current portal segments information based on what kind of "user" you are, but in reality, my problems involve information which might be found in many places, and I have to dig through all of them to find out where. It might be better if all information were contained in all portals, but organized differently. Right now, as a "new user & developer" I have a portal that's empty... not even a link to the faq! That's a big help! > This is a job that only DC can do right now. The ZDP has "only" got > the aim to point to existing stuff. Restructuring the existing docs > is not our job. Well, why is it called the Zope Documentation Project, if it's not supposed to provide documentation? Oh, wait... it's not, I guess. I hadn't looked at the title on http://zdp.zope.org before, but the link at http://www.zope.org/Documentation says it's project (and a source of documentation). > What documentation do you mean ? Well, there's the Zope Book project which requires lots of clicking (and it took me a little while to figure out that there was actually content on the sub-sections, because the interface changed on me). Personally, I haven't gotten any further, because I just started. -- Alan Shutko <ats(a)acm.org> - In a variety of flavors! 170 days, 17 hours, 37 minutes, 27 seconds till we run away. Your mind understands what you have been taught; your heart, what is true.

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RE: [Zope] Reloading products
by Seb Bacon 24 May '00

24 May '00

Shane pointed me to the Refresh product, but I'm still baffled. The same problem that's stopping me from updating my product is stopping the Refresh product from doing its thing on my product (even though it appears in the product folder itself). I can completely add or remove my own products from the Products directory and they have no effect whatsoever on the ZODB. Am I missing something? Here's what I'm doing to create a product (following source for various things including the Boring product): 1) create folder Products/AlbumImage 2) add __init__.py 3) in __init__.py, import AlbumImage, initialise(context) stuff 4) create AlbumImage/AlbumImage.py 5) do stuff that is good in AlbumImage.py Now, as far as I can tell, this should be sufficient to make my product appear in the products folder. Why does it refuse to disappear or change? Is it stuck somewhere in the ZODB? Eeeeek I'm confused. Seb. > -----Original Message----- > From: Chris Withers [mailto:chrisw@nipltd.com] > Sent: 24 May 2000 21:03 > To: Seb Bacon > Cc: Zope Users > Subject: Re: [Zope] Reloading products > > > Seb Bacon wrote: > >(n.b. is > > there any way of reloading a product without the tedium of > stopping and > > starting zope?) > > There is a very-alpha product for doing this floating around on the > zope-dev list. check the archives... > > Chris >

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RE: [Zope] 2.1.4 to 2.1.6 nightmare
by Brian Lloyd 24 May '00

24 May '00

> > Finally it works. Thanks. > > > > Do you know why DigitalCreations haven't release a patch? > > Dunno :S > > > I guess i'm not the first one getting mad with 2.1.6. > > Had us fooled for about a week :( > > I think it's all fixed in 2.2 anyway, which may be why no patch was > released... That's basically right - it boils down to that releasing a patch for every bug/feature just doesn't scale. We have made some internal adjustments to allow our release schedule to be much more flexible and frequent than it was, which should address this. Of course, if having every latest bug fix is of burning importance to you, you can run from the public CVS - though you are also, of course, going to get every latest bug as well :^) Brian Lloyd brian(a)digicool.com Software Engineer 540.371.6909 Digital Creations http://www.digicool.com

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