March 1999 - Zope - Zope lists

[ZDP] Assorted FAQs
by Martijn Faassen 04 Mar '99

04 Mar '99

Hi everybody, Here is a start. I just randomly browsed the mailing list and created a completely uncategorized set of questions and answers for the FAQ. I even snuck in a question of myself, see if you can answer it. :) If you see a problem with some of these questions or answers, send a followup with suggested corrections to the list and I'll include them in the FAQ. If you have more question/answer pairs, go ahead and followup too. I prefer these things to appear in the list (in a thread, and marked by [ZDP]) for now, as this might stop people from writing the same FAQs twice. I hope in a while we'll get somekind of collaborative FAQ environment going that makes all this easier. I'd prefer additions to the FAQ in StructuredText for now. See what follows for an example of the format I have in mind. If you think another format works better feel free to convert. (yes, that's the theme of open source; if you want something done differently, feel free to do the work to change it :). Here's what I have so far, enjoy! * How do I return an image from an External Method? Example (for a png image):: def foo(self, RESPONSE): # set the header RESPONSE['content-type'] = 'image/png' # return the actual image data return mkimage() Another way to set the header information is:: RESPONSE.setHeader('content-type','image/png') * How can an External Method refer to the objects in the Zope app? Use an External Method that gets passed 'self'. 'self' is your hook into Zope world. From 'self' you should be able to get anywhere you'd like to go. 'self' is the folder in which the external method is called. External Methods are methods of Folders. Since External Methods are acquired, self is not always the same Folder in which the method is defined--it may be a child Folder. * Is there any way for External Methods to access files on the filesystem of the server? An External Method can access anything on the server computer that the Zope process has access to. Therefore, an External Method can do just about anything a Python program can do. This is both a power and a liability. * Can I restrict what an External Method can do? Is there somekind of sandbox environment for External Methods? Right now there is no sandbox execution environment for External Methods. An External Method has access to everything that the Zope process has access to. This is one of the reasons why External Methods are required to be defined in the Extensions directory--it's easier to keep an eye on them there. * How do I call an external method from DTML? Use: &lt!--#var "external_method_name(arguments)"--&gt to call any External Method in the folder (or acquired by the folder). The more explicit alternative is: &lt!--#var expr="external_method_name(arguments)"--&gt The rule is that anything between double quotes in the first argument of the #var tag is interpreted as an expression attribute; a first argument without quotes is interpreted as a name attribute. * Why does StructuredText have trouble rendering the '#var' tags in the FAQ? Why do you use the HTML &amp escape codes in the FAQ when they don't work well either? I suspect there is some interaction between StructuredText and DTML that causes '#var' tags to be interpreted even when in a StructuredText code block (indicated by '::' or single quotes). I don't know any workaround right now, so I leave in ugly escape codes to encourage suggestions. :) * In a DTML expression, how do I access variable names with a '-' in them? (such as 'sequence-item') Any variable name (including those with '-') can be accessed in the '_' namespace. This contains a dictionary of all variables in the default namespace. To access 'sequence-item' you therefore use:: _['sequence-item'] * How do you safely do a backup of the Zope database? ('data.bbb' in the 'var' directory) In Zope 1.10 and later, you can simply back up the data.bbb. Because of the way the file written (all write operations are appends), it is highly unlikely for a backup file created directly to have a problem. If the database is being written while the file is being copied, then the Zope may discard the last transaction when reading the copy, if the last record is incomplete. Alternatively, you could export the entire site and backup the export file. This won't be a full backup however, as it won't contain old revisions of objects. Yet another alternative is to (mis)use the Pack operation (in the Zope Control Panel, database management). Pack will create a Data.bbb.old backup copy of your file before packing (for safety), which you could then back up. To exploit this side effect you could do a pack that says something ridiculous (like pack anything older than thousand days).

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ZDP's Ad-hoc Zope FAQ version 0.1
by Martijn Faassen 04 Mar '99

04 Mar '99

Hi everybody, Here is the new ad-hoc FAQ. I'll start versioning it as of now; this is version 0.1. How we'll do the actual versioning we'll still have to decide on, but at least we have a way to refer to this one now. Regards, Martijn ---- Note on the use of the Zope mailing lists: The Zope Documentation Project is getting its own mailing list (zdp(a)zope.org) In an attempt to gain publicity and support among the Zope community, I'll post this development FAQ to the main Zope list as well, however. Feel free to respond to it on either list for now, but you are encouraged to join the ZDP mailing list and to send new FAQ suggestions there. You can subscribe to the ZDP mailing list by using the page: http://www.zope.org/mailman/listinfo/zdp Note on the categorizing of this FAQ: This FAQ is a FAQ in progress. It is uncompletely unstructured, unrelated questions are mixed haphazardly. If you feel the calling to categorize the FAQ or to maintain the questions for a particular topic, feel free to mail your changes to the list, and thanks in advance! Note on the code examples and StructuredText: I've reconsidered and used normal '<' and '>' characters in sample DTML, for the reason that at least the FAQ is readable as text then. If you try to feed this FAQ through::  there will be an error message in Zope, however. For some reason Zope seems to try to interprete even StructuredText that uses &amp escape codes. Until this issue is resolved it is not possible to render this document into HTML. In my uninformed opinion, StructuredText code examples shouldn't be interpreted by Zope as actual DTML. There may be some rather subtle technical difficulties involved however. Any input on this is very welcome. Until the matter is resolved, the FAQ document will use StructuredText in the plaintext readable way. Thanks to Martijn Pieters in being so considerate to supply HTML escaped DTML examples; it's unfortunate his efforts weren't useful this time. Note on my availability: Martijn Faassen (me!), ad-hoc FAQ maintainer of the ZDP's Zope FAQ is generally not available to read or respond to email on friday, saturday and sunday. It is suggested ZDP related communication goes through the ZDP mailing list at zdp(a)zope.org anyway, and is not sent directly Martijn. This way anyone who wants to do something for the ZDP (such as editing and extending the FAQ) does not have to wait for Martijn to read his mail, having all relevant information available on the list. * How do I return an image from an External Method? Example (for a png image):: def foo(self, RESPONSE): # set the header RESPONSE['content-type'] = 'image/png' # return the actual image data return mkimage() Another way to set the header information is:: RESPONSE.setHeader('content-type','image/png') * How can an External Method refer to the objects in the Zope app? Use an External Method that gets passed 'self'. 'self' is your hook into Zope world. From 'self' you should be able to get anywhere you'd like to go. 'self' is the folder in which the external method is called. External Methods are methods of Folders. Since External Methods are acquired, self is not always the same Folder in which the method is defined--it may be a child Folder. * Is there any way for External Methods to access files on the filesystem of the server? An External Method can access anything on the server computer that the Zope process has access to. Therefore, an External Method can do just about anything a Python program can do. This is both a power and a liability. * Can I restrict what an External Method can do? Is there somekind of sandbox environment for External Methods? Right now there is no sandbox execution environment for External Methods. An External Method has access to everything that the Zope process has access to. This is one of the reasons why External Methods are required to be defined in the Extensions directory--it's easier to keep an eye on them there. * How do I call an external method from DTML? Use::  to call any External Method in the folder (or acquired by the folder). The more explicit alternative is::  The rule is that anything between double quotes in the first argument of the #var tag is interpreted as an expression attribute; a first argument without quotes is interpreted as a name attribute. * Why does StructuredText have trouble rendering the '#var' tags in the FAQ? Why do you use the HTML &amp escape codes in the FAQ when they don't work well either? I suspect there is some interaction between StructuredText and DTML that causes '#var' tags to be interpreted even when in a StructuredText code block (indicated by '::' or single quotes). I don't know any workaround right now, so I leave in ugly escape codes to encourage suggestions. :) * In a DTML expression, how do I access variable names with a '-' in them? (such as 'sequence-item') Any variable name (including those with '-') can be accessed in the '_' namespace. This contains a dictionary of all variables in the default namespace. To access 'sequence-item' you therefore use:: _['sequence-item'] * How do you safely do a backup of the Zope database? ('data.bbb' in the 'var' directory) In Zope 1.10 and later, you can simply back up the data.bbb. Because of the way the file written (all write operations are appends), it is highly unlikely for a backup file created directly to have a problem. If the database is being written while the file is being copied, then the Zope may discard the last transaction when reading the copy, if the last record is incomplete. Alternatively, you could export the entire site and backup the export file. This won't be a full backup however, as it won't contain old revisions of objects. Yet another alternative is to (mis)use the Pack operation (in the Zope Control Panel, database management). Pack will create a Data.bbb.old backup copy of your file before packing (for safety), which you could then back up. To exploit this side effect you could do a pack that says something ridiculous (like pack anything older than thousand days). * How do I pass a non-form variable to the next requested URL? Use Hidden fields within the form:: <input type="hidden" name="varname" value=""> * How do I define a variable for use in a document Set it in REQUEST::  * How do I tell the tree tag to show only Folders? By using the objectValues function in the branches_expr attribute of the tree tag. The objectValues function of a folder returns all objects contained by that folder. You can however, specify a list of object metatypes that it should return. objectValues(['DTML Document']) will only return all DTML Document objects in a Folder. Other metatypes you could select on are: Folder, DTML Method, File, Image, Mail Host, User Folder and Session. This is not a complete list, as Products can and will define their own metatypes. If you want to show more types, just add them to the list, like objValues(['Image', 'File']). Example of a Folder tree (with links to them)::  <A HREF="/">  </A>  * How can I collapse or expand a tree using a URL? The tree tag will show a tree fully expanded when the 'expand_all' variable is present in its namespace. So when a URL, showing a tree, is called with ?expand_all=1, the tree tag will expand all it's branches. Collapsing can be achieved with collapse_all. The following example shows a tree with collapse and expand 'buttons':: <A HREF="?expand_all=1"> Expand all</A>| <A HREF="?collapse_all=1"> Collapse all</A>  * How can I limit a tree to showing only *one* branch at a time? Use the 'single' attribute for your tree, like in::  * What is the difference between a DTML Method and a DTML Document? A DTML Method is what used to be just a Document in pre 1.10 releases. DTML Methods are not objects, they are methods. If you have a folder called 'foo', and it contained a DTML Method called 'bar', then 'bar' is a method of 'foo'. 'foo' doesn't contain the object 'bar', it has the method 'bar' bound to it. What this means is that from 'bar''s point of view, 'self' is a Folder object, and any properties it sees are properties of 'foo', not itself. DTML Documents are Zope Objects. Their idea of 'self' is themselves. They are contained in folders, but are not methods bound to that folder, they are instances of 'DTMLDocument.DTMLDocument'. They can manage their own Properties (because they inherit 'PropertyManager.PropertyManager'). Both DTML Documents and DTML Methods can hold DTML and content. The difference is subtle. DTML Methods would be used when the answer to the question "Am I showing some other objects content through me?" is Yes. DTML Documents should be used when the answer to the question "Am I the content I want to display?" is Yes. DTML Methods have the advantage that they don't have any properties, and their perspective of aquisition is from their containing folders point of view. DTML Documents have properties which may interfere with aquisition you'd want to do, and aquisition is from their own point of view, which may not be what you want. * How can I show all form data/cookies/REQUEST vars without knowing their names? By using the #in tag, you can easily all show all data in any dictionary object, like REQUEST.form, REQUEST.cookies and even REQUEST itself. Just call the items() method of the dictionary, and the #in tag will provide a sequence-key and sequence-item variable for every item in the dictionary. Show showing all form data can be done like this::  : <BR>  Use REQUEST.cookies.items() for all your cookies, and REQUEST.items() for all REQUEST variables, including CGI Environment variables. * What is a Principia Draft? It is a special use of the session object, but it appears to be partially broken. When you create a Principia Draft, it asks you to specify an orginal object, from the same Folder you are creating the Draft in. This will be your 'draft', on which you can make changes invisible to the outside world. The draft contains an invisible Session object that is immediatly started and joined, and an invisible UserFolder to facilitate extra users (for example, customers that want to be able to view your work on it as well, but have no access to it otherwise). The Principia Draft suffers two problems however. The first is really a Session object bug, in that security for Session objects is broken. The second problem is that the Userfolder and Session controls are inaccessible via the management screens. The latter problem is caused by convention changes in the Folder object (or the ObjectManager class really, used by Folder). I think that Folder objects *used* to call 'title_and_id' on a object when displaying it in it's management screen, but the current release of Zope constructs the id and title of an object by using its id and title separately. Principia Drafts made use of the call to 'title_and_id' to insert links to its UserFolder and Session controls. As this now doesn't happen anymore, you will have to do this yourself. As long as you have access to Session objects, you can change users on a Principia Draft object by calling it's 'users__draft__.manage_main' method, and reach the Session controls by calling its 'manage_approve__draft__' method. The URLS are:: http://yoursever.com/Zope/Draft/users__draft__/manage_main and:: http://yoursever.com/Zope/Draft/manage_approve__draft__

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[ZDP] List appears ready
by Robert OConnor 04 Mar '99

04 Mar '99

Hi Martijn, >I suggest to mail this list instead of me personally, so that other >people can respond friday and during the weekend, when I won't be around >to check the mail. We're working on getting a zdp(a)zope.org mailing list >too, but I can't say yet when that'll be ready. This ZDP list appears to be ready now although only Ken [List admin] is signed up. I added my name using: http://www.zope.org/mailman/listinfo/zdp The list of ZDP collaborators (subscribers) is at: http://www.zope.org/mailman/roster/zdp -bobo connor bob(a)rocnet.com

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RE: [Zope] [ZDP] Announcing the Zope Documentation Project
by Paul Everitt 04 Mar '99

04 Mar '99

Michael wrote: > Yes, at least theoretically. What would be covered and is > this an online > or offline course? My rough sketch right now is a four-day course: Day One -- Zope for Content Managers Day Two -- Zope Programming Using Zope Day Three -- Zope Programming Using Python Day Four -- Relational Databases and Zope -- Zope for System Administrators It would be a professionally produced and delivered "in the classroom" class, a la Learning Tree. That is, I won't be doing it. :^) Instead, I'll produce a poor version of the whole thing and give it to them, including the first customer that will send maybe 7 people. My poor version would probably become an online version. Just my thoughts currently. --Paul

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Query
by Dugas, Rheal 04 Mar '99

04 Mar '99

HI all I am a color specialist with Xerox. What i am doing with Zope is setting up a Knowedge database for my fellow color specialist. I am having a bit of a problem setting up a search query. Following is what i have know, Could somebody tell me how i could improve on this query. SELECT * FROM problems WHERE problems_rip_model LIKE  OR problems.prob_descript LIKE '%%' OR problems.prob_solution LIKE '%%' Is this the proper code or is there a better way of doing it? Thank You Rheal J. Dugas 1-800-939-3769 ext 1074

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Bobo or ZPublisher and stdout ( Solution: Client/Server)
by Dr. Armin Tschammer 04 Mar '99

04 Mar '99

Hi, I already sent some postings to this topic, but I would like to discuss the following problem again and how it could be solved. Imagine there is a big C++/Python project. The application is mainly prgrammed in C/C++ und one supports a scritpting interface to that application via the SWIG mechanism - the target language is Python. During the developping process many stuff is written to the stdout - during initialization ( before the main-function ), during execution ( in the main-function ), and in the destructors of the static instances ( after the main-function ). Now we want to do some web-stuff via ZPublisher, we define a function which return a html string, which is calculated through calling functions from our scritpting interface of our application, that means beside my correct calculated string there is many stuff sent to stdout, that confuses the Xserver and I get an error. Ok, you would say switch the stdout to a file via calling c-funcions like dup() or dup2( ) and encapsulate this in a function (wrapped via SWIG), which is called in the function which I call from the URL in the browser. Less cryptic: xy.py: start(): "XXXXXXX" #Now all stdout goes in a file stdout2file( "log.txt") .... HTMLstring = .... # sitches the stdout back ( REVerse ) # The way is free for CGI REVstdout2file() return HTMLstring the URL: http://myserver:3333/yyy/cgi-bin/xy/start BUT with this method I have no chance to chatch stuff which is written to the stdout in the destrutors of the static instances, because we already have switched back to the "usual" stdout (for a correctly working cgi-mechnism). The some problem one have with things which are written to the stdout during the initialisation of the static instances. ( Imagine python itself is compiled against a library which writes some stuff to stdout during initialization). I see only one solution: If there is a ZPublisher Server process which says to a client process do everything and give me a calculated string via sockets or something like that, I have not to take care about stuff which is written to the stdout at the client process. Or are there better solutions ? Thanks in advance, Armin

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RE: [Zope] [ZDP] Announcing the Zope Documentation Project
by Ken Manheimer 04 Mar '99

04 Mar '99

Martijn Faassen wrote: > Hereby I announce in absolute adhoc anarchistic fashion the Zope > Documentation Project. The Zope Documentation Project aims to generate > documention on anything Zope. Thank you, Martijn, you've made my day! This is extremely cool. As you might expect, here at digicool we're yearning to produce more and better documentation, and, as with other things, we want to have more time and energy to do it than we do. This kind of effort from you, and from anyone else who can help, is *severely* appreciated. I know i'll be participating - question is, besides scraping together the time we can, how else can digicool help? Some thoughts, below... > The Zope Documentation Project needs people who wants to help. It needs > these people to get organized. > > To get focused, I propose the ZDP's initial project is to provide FAQs > on various Zope topics. We can mine the mailing list for good questions > and answers. > > The ZDP asks everybody to contribute. Right now we need everything. :) > We need questions and answers, and we need to categorize these in > separate FAQ sections. We need Zope webspace somewhere to put up the > FAQ, I assume using the FAQ product. We need to develop the FAQ product > further, if necessary. We need whatever you can think of. > > The prime mean of communications for the ZDP is the Zope mailing list, > until further notice. I suggest that to keep the mailing list somewhat > organized we prepend our mailing list subjects with '[ZDP]'. If somebody > has a better way, we'll do it a better way. Some thoughts: - We would be happy to provide a mailing list or two for you all - If it makes sense (logistically, for us as well as for you), we could host the FAQ stuff or whatever on zope.org. This we'll have to discuss - both what all might want, and what we can safely and effectively do... (I've been thinking about requirements for a collaborative FAQ mechanism, which can be tricky if you want it to be available for contribution to the community in general, yet still remain organized enough for people to find what they're seeking. An interesting problem...) > > Note that while I'm sending out this message, I'm not anything official. > I'm just attempting to get the ball rolling. > > *nudges the ball* Yay! Ken klm(a)digicool.com

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[ZDP] Showing form data
by Martijn Pieters 04 Mar '99

04 Mar '99

* How can I show all form data/cookies/REQUEST vars without knowing their names? By using the #in tag, you can easily all show all data in any dictionary object, like REQUEST.form, REQUEST.cookies and even REQUEST itself. Just call the items() method of the dictionary, and the #in tag will provide a sequence-key and sequence-item variable for every item in the dictionary. Show showing all form data can be done like this::  : <BR>  Use REQUEST.cookies.items() for all your cookies, and REQUEST.items() for all REQUEST variables, including CGI Environment variables. -- M.J. Pieters, Web Developer | Antraciet http://www.antraciet.nl | Tel: +31-35-6254545 Fax: +31-35-6254555 | mailto:mj@antraciet.nl http://www.antraciet.nl/~mj | PGP: http://wwwkeys.nl.pgp.net:11371/pks/lookup?op=get&search=0xA8A32149 ------------------------------------------

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RE: [Zope] Some tough questions about zope... (long)
by Michel Pelletier 04 Mar '99

04 Mar '99

> -----Original Message----- > From: John Eikenberry [mailto:jae@kavi.com] > Sent: Wednesday, March 03, 1999 6:03 PM > To: Ronald Offerman > Cc: Michel Pelletier; Tony McDonald; zope(a)zope.org; > ron(a)heaven.rotflol.cx > Subject: Re: [Zope] Some tough questions about zope... (long) > > > On Wed, 3 Mar 1999, Ronald Offerman wrote: > > > > also a rather powerful language for being so simple). > Just leave your > > > PHP stuff in your documents; Zope will parse out the DTML > and return it > > > to the server, which will parse out the PHP stuff and > return it to the > > > browser. In fact, you can probably make DTML and PHP > work together > > > nicely and simplify much of your PHP code. In the > quickie case you > > > don't need to change your PHP. > > > > If this would work (having Apache parse the PHP code in the pages > > returned by Zope), you would save me a lot of painfull converting > > working PHP code (mainly database related) and I would > gradually convert > > from PHP/Apache to Zope/Python/Apache. > > This can't be done currently. I researched this a while back, > trying to > get server side includes to work. There's actually an entry > in the Apache > FAQ about it: > > """ > 9.How can I have my script output parsed? > > So you want to include SSI directives in the output from your CGI > script, but can't figure out how to do it? The short > answer is "you > can't." This is potentially a security liability and, more > importantly, it can not be cleanly implemented under the current > server API. The best workaround is for your script > itself to do what > the SSIs would be doing. After all, it's generating the > rest of the > content. > > This is a feature The Apache Group hopes to add in the next major > release after 1.3. > """ > > Though this is about SSI, it basically means (I believe) that > apache can't > take back the output of a CGI for additional module handling. > > --- Well paint me blue and call me a liar. At least it's planned. Michel > > John Eikenberry > [jae(a)kavi.com - http://taos.kavi.com/~jae/] > ______________________________________________________________ > "A society that will trade a little liberty for a little order > will deserve neither and lose both." > --B. Franklin > > > _______________________________________________ > Zope maillist - Zope(a)zope.org > http://www.zope.org/mailman/listinfo/zope >

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DTML Method vs Document
by Philip Aylesworth 04 Mar '99

04 Mar '99

I just upgraded to 1.10.2 and I noticed that when creating a new document I have a choice of DTML document and DTML method. This seems useful. I noticed that all my DTML documents and DTML methods have the icon for a DTML method. Everything seems to work. What is the difference between a DTML document and a DTML method? Seems to me a method should not be surfable but they are. Is it possible to change my documents to DTML documents? Even just for housekeeping. One other unrelated question: What is a Principia Draft? ------------------------------------------------------------------- Philip Aylesworth Information Systems Manager phila(a)regalint.com PGP public key: http://www.regalint.com/PGPkeys/phila.html

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