Mailman 3 April 2005 - Twisted-web

two questions abt nevow
by Little 25 Apr '05

25 Apr '05

I'm newbie now in Model-View-Controller pattern, from perl/php it's difficult to think in DOM-model :) So i have two questions, answers on which i can't google: Q1: I have a page. At page i have 2 elements. The values(data->render) of both elements must calculated from single request to the Database. Simple, it's looks like: [total: 100 rows] [table-like result] So, in the template i have 2 elements, with 2 data_functions: <div n:data="totals"> - ??? <div n:data="result"> - select * from db ... where ... But "totals" i will knew only after "result" makes request to DB So, i must to make "select * " in data_totals(), store data in self.var, and take it from self.var in data_result() function. This way is not perfect to me, coz if request to DB failed - it's very difficult to pass message about error into "request" function. May be not difficult but not clear. :( Another way is to use "fake" tag before "totals" and "request", like this: <n:invisible data="real_request"> <div n:data="fetch_totals"> <div n:data="fetch_data"> Where data_real_request() doing "select *" and stores result (or error msg) in self.var It's not perfect too, coz we have program logic layer in template, and, again, it's not clear to programmer. Third way is to use 2 requests to DB - the worst way, coz requests are long in time. Is there another, perfect, clear way to produce such pages in nevow? Q2: About formless. How can i use my own check of form element's value? For example, i have "e-mail" field in form. And i wanna check char '@' existense in it. When my code falls into anotate.autocallable() function in FormImplementation class - i have only values of form elements. If e-mail value doesn't have "@"-char, how can i stop submitting and show error near "e-mail" field in form when RenderForm() called?

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Fetching RSS data for my app
by Dustin Sallings 25 Apr '05

25 Apr '05

I hope this question doesn't fall too far out of the scope of twisted-web, but it seems like the best place to start. Basically, I have an application that is a tcp server (using service.Application and internet.TCPServer). I'd like to additionally have a scheduled check of some RSS feeds such that data retrieved from the RSS feeds is saved in a sort of singleton dict I can access from other parts of my application. I had thought that the ``twisted.web.monitor'' looked like a good start, except I can't get that to compile: % pydoc twisted.web.monitor problem in /System/Library/Frameworks/Python.framework/Versions/2.3/lib/python2.3/ site-packages/twisted/web/monitor.pyc - AttributeError: class IChangeNotified has no attribute '__class__' Can someone give me some guidance as to what the best way to accomplish what I think I want to accomplish is, as well as how I add this into my application? Thanks. -- Dustin Sallings

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pointers for newbie
by gerardo arnaez 24 Apr '05

24 Apr '05

hi all I have started reading the docs. limited python experience. After having googled and spoken on twisted.web and #python I am going to try to use nevow to set this up The main code works and can be used to calculate coumadin ( a medicine ) dosing working code is at http://mung.net/c.html I know want to translate this to a web page. to allow easier access. Any pointers or ideas are helpful. Have no experience in this so need so clue-batting. Thanks all

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livepage error
by Christopher Zorn 18 Apr '05

18 Apr '05

Hello, I am getting a strange error with livepage In a rend.Page class I have the following def render_body(self, ctx, data): realm, mind = data def unload(client): print "unload" return ctx.tag(onunload=livepage.handler(unload)) This worked before, but now I get the following Exception : twisted.python.components.CannotAdapt: WovenContext(tag=None, isAttrib=True) to <MetaInterface nevow.livepage.IClientHandle> If more detail is needed please let me know.

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Nevow trunk
by James Y Knight 18 Apr '05

18 Apr '05

Just a note for those not following commits closely: Nevow trunk (what will become 0.5) now requires zope-interface, and twisted 2.0. For anyone trying to use Nevow without twisted installed at all, it's supposed to still work without twisted installed at all, but only if you convert your app to zope-interface style declarations, rather than twisted1.3 __implements__ style. Also, I don't know that anyone's tested it like that, so it probably doesn't work right now. Also, if you get an error like this: exceptions.TypeError: _interface_coptimizations.SpecificationBase.__new__(MetaTypedInterface) is not safe, use object.__new__() that means your zope-interface package is 3.0, which is buggy, and you should install 3.0.1. James

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Uploading large files to a Twisted-webserver?
by Thomas Weholt 18 Apr '05

18 Apr '05

Hi, I need to be able to upload large files ( 6-10MB ) to a web-server using Twisted. I've read somewhere that Twisted limits the size of uploads to 600kb to avoid hacking/crashes whatever, but I need to be able to upload files this big. Any clues or hints are welcome, but it must standard HTTP and one single port. The only other option I could be interested in is setting up a simple FTP-server running in the same process as the webserver, but I've never got that working using Twisted. -- Mvh/Best regards, Thomas Weholt http://www.weholt.org

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Efficient server-side web-scraping?
by Tom Locke 18 Apr '05

18 Apr '05

Hi, I've developed a small Python CGI app which I'm porting to Twisted Web in order to add some in-memory caching. The app (you can see the current version at etrays.net) sticks a bunch of hits from the ebay advanced search into a box for folks to stick on their site. The server makes an HTTP request to the eBay search form, and scrapes the result using Beautiful Soup. Right now, I simply do all the work in a .rpy script. If I've understood Twisted correctly, the whole server blocks while my render_GET method runs, right. (Twisted is single threaded) So the search on eBay blocks Twisted (I just call urllib.urlopen) which is bad because it's pretty slow. Could anyone suggest a setup where the eBay search can take place in the background, leaving twisted free to process other incoming requests. When the eBay results come back, the corresponding Twisted request would wake up, scrape the HTML and complete. I guess I need to use threads here? And have a Twisted callback triggered when the thread completes? Thanks Tom.

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freeform and adbapi
by Stephan Cieszynski 18 Apr '05

18 Apr '05

Hello *. I want to validate forminput against a database. For this reason, i wrote my own class: class Username(annotate.Typed): def coerce (self, val, configurable): [some code] def _eb(r): raise annotate.InputError('database error') # this works very well: # def _cb(r, val): # if len(r): # return r[0][0] # return '' # if the username already in use, i want to raise an exception: # the errormessage isn't placed correct in the rendered # 'form'page, but the whole exceptionpage is filled in # in the slot('error') of this input field def _cb(r, val): if len(r): raise annotate.InputError("username in use") return val d = dbpool.runQuery("""SELECT username FROM userdb WHERE username = %s""", str(val)) d.addCallback(_cb, val) d.addErrback(_eb) return d dbpool.runQuery returns a deferred. If i want to use the username returned by the query, the result is placed correctly in the formfield. But if an exception raised (here: InputError), the delay by the deferred is to long and the whole exceptionpage is placed in the slot('error'), not the message ('username in use') only. Is my way right? Is there a way to solve this problem? Stephan

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web2 vs. access.log
by Tommi Virtanen 15 Apr '05

15 Apr '05

Hi. I'm trying to hack vhost-specific access.log (.../vhost/canonicalhostnamehere.log) support into nevow, and while doing that, ran into web2's logging features -- I don't want to do things totally differently from web2. What I did with nevow was add ILogger, which is looked up from the context and is responsible for writing the access.log entry for the current request. Thus, vhosts can just remember an ILogger to implement different access log destinations. What web2 seems to be heading at is using log.msg and a interface=IRequest to do access.logging. How do you see my vhost logging functionality should be done with web2? Adding observers doesn't really help, AFAICS the best you could do that way is log the request in both the default access.log and the vhost log file. Also, web2 really should pass the context to log.msg(). Also, how do you feel the date and time generation and parsing in t.w.http should be done? I need to be able to generate access.log entries, and current t.w.http really isn't librarified enough. I'm thinking of extracting that functionality in a more library-like manner into nevow.timestamp and nevow.log, which could at the same time become t.web2.{timestamp,log}.

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backport if-modified-since bugfix from web2 to web
by Stefano Debenedetti 12 Apr '05

12 Apr '05

Hello, As noted in a web2 docstring: # Ancient versions of netscape and *current* versions of MSIE send # If-Modified-Since: Thu, 05 Aug2004 12:57:27 GMT; length=123 # which is blantantly RFC-violating and not documented anywhere While we wait for web2, the attached patch [1] against SVN trunk revision13528 makes twisted.web fix the issue the same way as twisted.web2. ciao ste [1] http://twistedmatrix.com/bugs/issue976

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