Re: [Zope] Trapping zope exceptions in python script
--On 15. Dezember 2005 08:03:22 -0500 Jonathan [EMAIL PROTECTED] wrote: - Original Message - From: J Cameron Cooper It seems strange that one can, using plain vanilla python scripts, trap bare 'try/excepts' (and I agree with Andreas that this is not a good thing to do!) and that one can trap python built-in exceptions, but that one cannot trap zope exceptions. Why allow python scripts to trap zope exceptions using a bare try/except (and then have to re-raise everything except the target zope exception), but not allow python scripts to target specific zope exceptions? I don't see the reasoning behind this approach. My 2 cents: PythonScripts are restricted and are *not* thought to be a full replacement for Python modules. If you need this functionaltiy consider writing a Zope Product, using external methods or using TrustedExecutables. -aj pgpQyEjsXil5w.pgp Description: PGP signature ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Jonathan schrieb: ... It seems strange that one can, using plain vanilla python scripts, trap bare 'try/excepts' (and I agree with Andreas that this is not a good thing to do!) and that one can trap python built-in exceptions, but that one cannot trap zope exceptions. Why allow python scripts to trap zope exceptions using a bare try/except (and then have to re-raise everything except the target zope exception), but not allow python scripts to target specific zope exceptions? I don't see the reasoning behind this approach. Well you can trap any exception which happens between your try and except. But not outside of these, of course. This is true everywhere (not even python only ;) Which exceptions do you believe you might be not able to catch? HTH Tino ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
- Original Message - From: Tino Wildenhain [EMAIL PROTECTED] To: Jonathan [EMAIL PROTECTED] Cc: zope@zope.org Sent: Thursday, December 15, 2005 8:18 AM Subject: Re: [Zope] Trapping zope exceptions in python script Jonathan schrieb: ... It seems strange that one can, using plain vanilla python scripts, trap bare 'try/excepts' (and I agree with Andreas that this is not a good thing to do!) and that one can trap python built-in exceptions, but that one cannot trap zope exceptions. Why allow python scripts to trap zope exceptions using a bare try/except (and then have to re-raise everything except the target zope exception), but not allow python scripts to target specific zope exceptions? I don't see the reasoning behind this approach. Well you can trap any exception which happens between your try and except. But not outside of these, of course. This is true everywhere (not even python only ;) Which exceptions do you believe you might be not able to catch? I encountered this situation while trying to trap 'BadRequest'. Jonathan ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Andreas wrote: My 2 cents: PythonScripts are restricted and are *not* thought to be a full replacement for Python modules. If you need this functionaltiy consider writing a Zope Product, using external methods or using TrustedExecutables. If python scripts are restricted from accessing zExceptions (for security reasons???) then why allow python scripts to trap zExceptions in bare try/excepts? If the logic for not allowing zExceptions in plain vanilla python scripts is for security reasons, then allowing bare try/excepts would seem to be a security hole (though, I don't see the rationale for this). My 2 cents. Jonathan ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
... Try: context.afolder.manage_delObjects(['someitem']) where 'someitem' does not exist in 'afolder' works: try: context.afolder.manage_adlObjects(['nonexistent']) except Exception,x: if 'BadRequest' in repr(x): print bad request else: raise x :-) (Ok, this _is_ ugly, but at least works. Certainly these exception types should be importable or even immediately available for python scripts) ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
- Original Message - From: Tino Wildenhain [EMAIL PROTECTED] To: Jonathan [EMAIL PROTECTED]; zope@zope.org Sent: Thursday, December 15, 2005 8:48 AM Subject: Re: [Zope] Trapping zope exceptions in python script ... Try: context.afolder.manage_delObjects(['someitem']) where 'someitem' does not exist in 'afolder' works: try: context.afolder.manage_adlObjects(['nonexistent']) except Exception,x: if 'BadRequest' in repr(x): print bad request else: raise x :-) (Ok, this _is_ ugly, but at least works. Certainly these exception types should be importable or even immediately available for python scripts) Interesting work-around, but I agree that these exception types should be immediately available in plain vanilla python scripts. Jonathan ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
--On 15. Dezember 2005 09:08:20 -0500 Jonathan [EMAIL PROTECTED] wrote: - Original Message - From: Tino Wildenhain [EMAIL PROTECTED] Interesting work-around, but I agree that these exception types should be immediately available in plain vanilla python scripts. Patches + tests are welcome :-) -aj pgp4Ivu8J9Dnz.pgp Description: PGP signature ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Andreas Jung schrieb: --On 15. Dezember 2005 09:08:20 -0500 Jonathan [EMAIL PROTECTED] wrote: - Original Message - From: Tino Wildenhain [EMAIL PROTECTED] Interesting work-around, but I agree that these exception types should be immediately available in plain vanilla python scripts. Patches + tests are welcome :-) Yes, Jonathan: please file a bug report - best with a list of Exceptions to be made available :-) ++Tino ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Jonathan wrote: Andreas wrote: My 2 cents: PythonScripts are restricted and are *not* thought to be a full replacement for Python modules. If you need this functionaltiy consider writing a Zope Product, using external methods or using TrustedExecutables. If python scripts are restricted from accessing zExceptions (for security reasons???) then why allow python scripts to trap zExceptions in bare try/excepts? If the logic for not allowing zExceptions in plain vanilla python scripts is for security reasons, then allowing bare try/excepts would seem to be a security hole (though, I don't see the rationale for this). I would imagine that not allowing these exceptions to be imported in trusted code is simply an oversight. The mechanism involved is not a you may not import this type of thing, but rather a you may import this statement. It is easy to miss safe but rarely used pieces. If you have a list of exceptions you would like to have available, go and file a bug report. A patch would be even better. --jcc -- Building Websites with Plone http://plonebook.packtpub.com/ Enfold Systems, LLC http://www.enfoldsystems.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Andreas Jung wrote: --On 14. Dezember 2005 12:54:56 -0700 Nikko Wolf [EMAIL PROTECTED] wrote: So you could try this instead: for item in itemList: try: context.afolder.manage_delObjects([item]) except: continue Wa... DON'T DO THAT. You should *never* use bare try..excepts within Zope applications. This can lead to strange and unpredictable behavior. Can you elaborate on what strange and unpredictable behavior you mean? I'm curious in general, but especially w.r.t. the code above? BTW, a simple grep of sources in Zope (2.7.6-final) turns up 600+ places where a bare except is used, and my Zope instance (which uses Plone) contains over 350 more. Cheers, Nikko ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
On Dec 15, 2005, at 4:01 PM, Nikko Wolf wrote: Can you elaborate on what strange and unpredictable behavior you mean? I'm curious in general, but especially w.r.t. the code above? BTW, a simple grep of sources in Zope (2.7.6-final) turns up 600+ places where a bare except is used, and my Zope instance (which uses Plone) contains over 350 more. Often when you see a bare except, it is after some of the specific important exceptions are caught and re-raised: try: something() except ConflictError: raise except: recover() Even this is pretty poor style anyway (If you don't know enough about what is going wrong to know what is being thrown, you probably shouldn't be in charge of recovering from it.) The problem with catching and swallowing ConflictError and similar internal Zope errors is that you leave your ZODB in an inconsistent state. Roughly, one request has started making modifications to the ZODB, then a second request has been making modifications to the same object. The ZODB has noticed this, and throws this ConflictError exception. It is expecting this exception to bubble up all the way out of your code, throwing away whatever potential modifications you have made to the ZODB and having Zope try your code again. (at that point, hopefully the task that didn't get the conflict error has completed and committed its changes. When your code is run again, it will see the new values from the other transaction. Here an (again very rough) example: Imagine that you have two collections of objects called unprocessed and processed. A group of somethings or someones grab the next item in unprocessed, and puts it into processed. If two requests come in to grab the next item from unprocessed and put it one of the other buckets, at some point. one or both of them will get the ConflictError exception. If the exception is swallowed by the code both of them will save their copy of the object in processed, and where you had one object before you now have two. If these objects were student quizzes, two copies of the same quiz will double the weight of the score. If these object were loan application, the amount of money you were paying out has doubled. All around bad news. ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
[Zope] Trapping zope exceptions in python script
I am trying to catch a 'BadRequest' exception in the following python script excerpt: for item in itemList: try: context.afolder.manage_delObjects([item]) except BadRequest: continue The rationale behind this is that itemList may contain entries that no longer exist in 'afolder', but I would like to delete whatever does exist. 'BadRequest' is not a python built-in exception, so whenever the above except clause is invoked it actually causes another error: Traceback (innermost last): Module ZPublisher.Publish, line 98, in publish Module ZPublisher.mapply, line 88, in mapply Module ZPublisher.Publish, line 39, in call_object Module OFS.DTMLMethod, line 126, in __call__ Module DocumentTemplate.DT_String, line 474, in __call__ Module DocumentTemplate.DT_In, line 705, in renderwob Module DocumentTemplate.DT_Util, line 201, in eval - __traceback_info__: _ Module string, line 2, in f Module Shared.DC.Scripts.Bindings, line 252, in __call__ Module Shared.DC.Scripts.Bindings, line 283, in _bindAndExec Module Products.PythonScripts.PythonScript, line 315, in _exec Module Script (Python), line 25, in subDeleteAd - PythonScript at /fas/subDeleteAd - Line 25 NameError: global name 'BadRequest' is not defined I can work around this problem by checking to see if the item exists in 'afolder' before I try to delete it, but I was curious as to how you go about trapping a 'BadRequest' error in a python script? Thanks, Jonathan ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Jonathan wrote: I am trying to catch a 'BadRequest' exception in the following python script excerpt: for item in itemList: try: context.afolder.manage_delObjects([item]) except BadRequest: continue NameError: global name 'BadRequest' is not defined The following would normally be required, but it fails with an ImportError: from zExceptions import BadRequest So you could try this instead: for item in itemList: try: context.afolder.manage_delObjects([item]) except: continue In general, TTW coding is very limited; you can use External Methods (a.k.a. Extensions) or Products to avoid this. ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
--On 14. Dezember 2005 12:54:56 -0700 Nikko Wolf [EMAIL PROTECTED] wrote: So you could try this instead: for item in itemList: try: context.afolder.manage_delObjects([item]) except: continue Wa... DON'T DO THAT. You should *never* use bare try..excepts within Zope applications. This can lead to strange and unpredictable behavior. -aj pgpfQQjIMbwun.pgp Description: PGP signature ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Thanks to everyone for the feedback... the bottom line seems to be that you can NOT trap zope exceptions in a python script... which seems a bit odd. Jonathan - Original Message - From: Andreas Jung [EMAIL PROTECTED] To: Nikko Wolf [EMAIL PROTECTED]; zope@zope.org Sent: Wednesday, December 14, 2005 3:06 PM Subject: Re: [Zope] Trapping zope exceptions in python script ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev ) ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Am Mittwoch, den 14.12.2005, 16:20 -0500 schrieb Jonathan: Thanks to everyone for the feedback... the bottom line seems to be that you can NOT trap zope exceptions in a python script... which seems a bit odd. No, you can. But you should know what you do and reraise critical (e.g. Conflict exeptions and the like). ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
Jonathan wrote: Thanks to everyone for the feedback... the bottom line seems to be that you can NOT trap zope exceptions in a python script... which seems a bit odd. Of course you can. You just are restricted from importing certain things, which happens to include this class of exception. Probably it is safe for Zope to allow importing this in restricted code; feel free to file a bug report. But you have easy avenues to deal with this: either declare that class safe for import or take a couple extra seconds and write it in an External Method. --jcc -- Building Websites with Plone http://plonebook.packtpub.com/ Enfold Systems, LLC http://www.enfoldsystems.com ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
Re: [Zope] Trapping zope exceptions in python script
--On 14. Dezember 2005 16:20:57 -0500 Jonathan [EMAIL PROTECTED] wrote: Thanks to everyone for the feedback... the bottom line seems to be that you can NOT trap zope exceptions in a python script... which seems a bit odd. Nothing is odd. I just told you to avoid *bare* try..excepts..as Tino pointed out you should must reraise re-raise excepctions like ConflictErrors. Otherwise if you don#t know what you're doing, don't use bare try...excepts. -aj pgpKwTfDJEqDB.pgp Description: PGP signature ___ Zope maillist - Zope@zope.org http://mail.zope.org/mailman/listinfo/zope ** No cross posts or HTML encoding! ** (Related lists - http://mail.zope.org/mailman/listinfo/zope-announce http://mail.zope.org/mailman/listinfo/zope-dev )
