October 2000 - Zope-Dev

Special Method's
by Andre Schubert 27 Oct '00

27 Oct '00

Hi, I have a question on special methods in python. I want to program a product that has many methods. I anyone anywhere is calling one of these methods a other method should be called before. Is there a special method name or is there a way to perform this? as

1 0

Documentation Documentation on dev.zope.org
by Amos Latteier 26 Oct '00

26 Oct '00

Hello Zope Developers, I've added two documents to dev.zope.org How to Document Your Zope Product http://dev.zope.org/Documentation/DocsProcedures/ProductDoc How to Document Your Changes to Zope http://dev.zope.org/Documentation/DocsProcedures/ZopeChanges They are wikis so dive in and add your 2 cents. -Amos -- Amos Latteier mailto:amos@digicool.com Digital Creations http://www.digicool.com

1 0

Flat Database/ZPatterns api, performance ?
by Simon Michael 26 Oct '00

26 Oct '00

Flat Database (was ListMate) is just what I need to whip up an interface for non-technical administrators - thanks. So I migrated two data tables ("workshops" & "registrations") from gadfly to flatdb instances using the CSV import feature, and the admin interface is working fine. I'm having a hard time, though, figuring out how to access the data programmatically. I scavenged the docs (zpatterns wiki very helpful, as far as it went; not much available for flatdb), searched the lists (nothing) and grovelled around in the code. I'd appreciate any comments or advice on the following. 1. how can I look up a row in the table by column value, other than searching the whole table: ? <dtml-in "workshops.entryValues()"> <dtml-if "getProperty('col_workshopid') == workshop"> <dtml-var "getProperty('col_description')"> </dtml-if> </dtml-in> 2. how can I add an entry to a table ? I tried this: <dtml-let entry="registrations.manage_addEntry()"> <dtml-call "entry.manage_addProperty('col_workshopid','string','TEST')"> <dtml-call "entry.manage_addProperty('col_firstname','string','TEST')"> <dtml-call "entry.manage_addProperty('col_lastname','string','TEST')"> ... </dtml-let> and it seems to create a number of spurious rows with only the first field set. This didn't work either: <dtml-call "registrations.manage_addEntry().manage_changeProperties( col_workshopid='TEST', col_firstname='TEST', col_lastname='TEST', ... )"> 3. displaying table contents seems quite slow. On this P100 with 48Mb ram doing nothing but zope, no load and generally snappy, generating the 50-row, 20-column registrations table listing takes 15 seconds. Any ideas about where this comes from ? 4. this is my first encounter with the mighty zpatterns. I wonder how one might add a thing (data plugin ?) so that FlatDb could read the data out of zgadfly or something faster, instead of migrating it as I did ? Many thanks! -Simon

2 1

Path Handler problems
by Chris Withers 26 Oct '00

26 Oct '00

Hi, I've finally gotten around to doing the PathHandler product I mentioned ages ago and now I've run into problems. Since it's so short, here's the product class: class PathHandler( SimpleItem,Persistent,Acquisition.Implicit ): meta_type = 'Path Handler' def __init__(self, id, method_name, title=''): """initialise a new instance of Path Handler""" self.id = id self.title = title self.method_name= method_name def __bobo_traverse__(self, TraversalRequest, name): list=copy(TraversalRequest['TraversalRequestNameStack']) list.reverse() TraversalRequest['path_to_handle']=[name]+list TraversalRequest['TraversalRequestNameStack']=[] return getattr(self,self.method_name) Okay, the confusing bit first. Let's say x is an instance of PathHandler, with method_name = 'the_method'. the_method is a DTML method as follows: <dtml-var standard_html_header> <h2><dtml-var title_or_id> <dtml-var document_title></h2> <p> <dtml-var path_to_handle> </p> <dtml-var standard_html_footer> If I try the url: http://localhost:7080/x ...I get: Resource not found  Traceback (innermost last): File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 222, in publish_module File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 187, in publish File E:\Zope\2271B4~1.2\lib\python\Zope\__init__.py, line 221, in zpublisher_exception_hook (Object: ApplicationDefaultPermissions) File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 173, in publish File E:\Zope\2271B4~1.2\lib\python\ZPublisher\HTTPResponse.py, line 308, in setBody File E:\Zope\2271B4~1.2\lib\python\ZPublisher\HTTPResponse.py, line 529, in notFoundError NotFound: (see above) If I try the url: http://localhost:7080/x/1 ...I get what I expect, the output of the_method, with path_to_handle set to ['1'] Now, if I try the following url or anythong longer: http://localhost:7080/x/1/2 ...I get: Zope has encountered a problem publishing your object. Cannot locate object at: http://localhost:7080/x/1/2 Traceback (innermost last): File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 222, in publish_module File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 187, in publish File E:\Zope\2271B4~1.2\lib\python\Zope\__init__.py, line 221, in zpublisher_exception_hook (Object: the_method) File E:\Zope\2271B4~1.2\lib\python\ZPublisher\Publish.py, line 162, in publish File E:\Zope\2271B4~1.2\lib\python\ZPublisher\BaseRequest.py, line 367, in traverse File E:\Zope\2271B4~1.2\lib\python\ZPublisher\HTTPResponse.py, line 539, in debugError NotFound: (see above) Can anyone (Evan?) suggest what's going on here and what I need to do to fix it? cheers, Chris

1 0

RE: [Zope-dev] Michel's Reply
by Toby Dickenson 26 Oct '00

26 Oct '00

> I'm not sure I grok what rightness has to do about it. I > think this is > right, to me wrong == broken. This is not broken. Let me persuade you. > > * someone adds an property named feed to an object at an > intermediate > > location in the containment heirarchy. This breaks the cron job that > > calls self.Zoo.Diet.LargeAnimals.hippo.feed(), and all the hippos > > starve. > > This is the classic anti-acquisition argument, but it's a red > herring. I used to believe that too, but no longer agree. I changed my mind after developing a large application in Zope, and spending alot of time firefighting the problems that it caused. > The same argument applies to inheritance; introducing an attribute > between two classes in a generalized relationship and your app breaks > and all the hippos starve anyway. This analogy is false. If a programmer is responsible for a class and it becomes broken in that way then yes, he is at fault. Fortunately there are well understood principles for design inheritance relationships to keep this easy. Each project has a finite number of classes. Each class has dependencies to only a small number of other classes. Testing (is used appropriately) can be used to ensure correctness, and this probably means re-testing each derived class when a base class changes. The same is not true of a containment heirarchy. The containment heirarchy is managed by content managers, who are responsible for content. After adding content they might test that content, but they are unlikely to retest any functionality - its not their responsibility. The containment heirarchy is often large and sprawling. Acquisition-based bugs occur on a per-instance basis, not per-class, and typically there will be very many more instances in a system than there are classes. After a change to an instance there is a need to re-test *every* *instance* below the change in the containment heirachy. (When was the last time you changed your root folder? Did you test your whole site?). This makes it impractical to test them all. You raised the question of whether this is an anti-acquisition argument or a containtment-vs-context-binding argument. Please dont misunderstand me; acquisition is great when used appropriately. However if methods bound to containement then acquisition could not be used for the purpose you are demonstrating here. > Zope cannot be robust against > programmer error. Nothing can. I, as a programmer, develop Zope products. My users install them on their system. If your users are programmers then this comment is relevant, but I dont. Adding a property to an object (using the Property tab in the management interface) is a user-level operation. I do expect my systems to be robust against user error. (Note that it is even possible to 'break' Zope's own management interface by adding some carefully named properties. Some of those are even WikiNames ;-) > > * someone uses self.Zoo.Diet.buildings.visitor_reception.feed(), and > > ends up filling the reception with hippo food. (This might even be > > possible for someone who has no permissions on the reception object) > > This is once again programmer error. Do you mean the programmer who implemented 'feed'? If yes, Im pleased you agree with me. Their mistake was to use acquisition instead of inheritance. If they wanted to use acquistion then they would need to augment their otherwise simple implementation of 'feed' with either: 1. Explicit security checks (hard to get right) 2. Explicit is_instance checks (inflexible) 3. Accept the fact that anyone granted the 'Feed Hippos' permission on any hippo may dump hippo feed anywhere, or feed other hippos for which they do not have that permission. Perhaps the hippo analogy isnt helping, so heres a more concrete example. In zope today it is possible for a user who has been granted the 'View Management Screens' permission in *one* folder to create a one-line dtml method that lets him see the management page of any other dtml method in the whole site. Why? because DTMLMethod's manage_main binds to context not containment. > > * someone uses > > > self.Zoo.buildings.office.printers.laserjet1.Zoo.Diet.LargeAni > mals.hippo.feed(), > > and ends up feeding paper to the hippo. (that could even be someone > > who has no other permisions on that hippo object) > > This is the same as your first two arguments: programmer error. (Note: Michel is right that this one is not immediately relevant to the binding discussion; its purely a demonstration of a misuse of acquisition. Its also a programmer error, but in Michel is that programmer) The real problem here is that you are relying on acquisition from a context that is not a direct container. Each instance only has one containment heirarchy. However it has an infinite number of possible contexts, which are chosen by the caller. Suppose you have an (apparently correct) external method in Zoo: def feeding_time(self): self.Diet.LargeAnimals.hippo.feed() A malicious user browses to /Zoo/buildings/office/laserjet1/feeding_time. The problem is that acquisition from context outside the containment heirarchy doesnt do what you expect. When the external method looks for the 'feed' attribute it will actually find it from the printer object. This allows a malicious user to call methods on the printer object to which he does not have permission. Jim (if you read this far): Was there a good reason why acquisition needed to look anywhere other than containment heirarchy? > > Ive now nearly finished converting all my newbie zope > projects back to > > a conventional O-O design. I have been bitten by all the problems > > listed above. The feed method *should* *be* implemented in > a ZooAnimal > > base class. > > Ok, that's a valid approach. Can you explain any advantage of the approach you are advocating?

4 5

RE: [Zope-dev] Bindings and Votings
by Toby Dickenson 26 Oct '00

26 Oct '00

> ...but can you bind self to the context or, more perversely, > context to > the container? As the first line in your PythonMethod: self,context = context,self But why would you want to?

2 1

How to use methods in a deeper folder?
by Loibl Johann 26 Oct '00

26 Oct '00

Hi, I would like to use a SQL-Method which exists in a deeper folder; e.g. in dtml-Method /eins/zwei/index_html there exists <dtml-in "/eins/zwei/drei/sqlMethod"> <dtml-var something> </dtml-in> and my sqlMethod is situated in folder /eins/zwei/drei/ Why doesn't this work? Could someone give me a helping hand? Cheers, Hannes

2 1

Re: [Zope-dev] 2 Zopes
by Gregor Heine 26 Oct '00

26 Oct '00

> > Hi, > > > > Can anyone tell me a way to get Zope Objects from the first > > Zope-Installation to the second. > > I need this because i have to program a Product to putting data into > > different Zope Installations from one point of the Web. > > My boss want this way because he want a central point for data input, > > where the data are of different type and therefore they have to stored > > in different locations( different Zope Installations) My idea is to use > > ZPublisher.Client, but i don't find a way to use it. > > > > thanks as > > if you need to copy the actual objects verbatim you might want to > investigate exporting to zexp and using file transfer between the hosts > and (using Client to faciltate calling into zope) importing them on the > second server. > The Client/Server Product is probably doing exactly what you want. It uses the Zope Export/Import facility to transfer whole objects from one Zope to another. You find it at www.zope.org/Members/MacGregor/Client_Server maybe you give it a try :) Cheers, Gregor!

1 0

Re: [Zope-dev] Migrating from ZClasses to Python Products
by Jason Spisak 25 Oct '00

25 Oct '00

Ender writes: Point taken. > Jason Spisak wrote: > > > > Ender writes: > > > > > Jason Spisak wrote: > > > > > > > > The only problem I am dealing with is size. > > > > What kind of a transaction will that be? > > > > Huge, no doubt. > > > > > > > > I would run out of space to buffer it. Does Zope do subtransactions now, > > > > or is that still just the ZCatalog? > > > > > > zope has done subtransactions for a while, i'm not sure if this predates > > > zcatalog or not ( i assume'd it does). > > > > > > just call get_transaction.commit(1) to save work. and call > > > get_tranaction.commit() when you're done. i'm in the process of writing > > > an advanced transaction how-to which will hopefully give some more > > > enlightenment on this process, but i've been busy with work so i don't > > > expect to have it public for another week. > > > > > > > Also, I am running on stock RH6.2 linux and to double my ZODB puts me near > > > > the 2 gig file limit. Not as much of a concern as a pain in my neck. Is > > > > it faster to modify my installation to allow > 2GB or create from > > > > xml/export? > > > > > > you could create the python product instances in a mounted db. > > > > > > > I looked into this. The webpage is very exclamitory about it's volitility, > > and yet Zope.org uses it. Worth a shot. > > do make a backup, i hosed something in my zodb using it. > > kapil Jason Spisak

1 0

2 Zopes
by Andre Schubert 25 Oct '00

25 Oct '00

Hi, Can anyone tell me a way to get Zope Objects from the first Zope-Installation to the second. I need this because i have to program a Product to putting data into different Zope Installations from one point of the Web. My boss want this way because he want a central point for data input, where the data are of different type and therefore they have to stored in different locations( different Zope Installations) My idea is to use ZPublisher.Client, but i don't find a way to use it. thanks as

3 2