On Nov 2, 11:19 pm, "Diez B. Roggisch" <[EMAIL PROTECTED]> wrote:
> Push-style though enhances the risk of mixing program logic with > presentation-logic (as simple print-statements do), and makes it a > precondition that anybody who's supposed to tinker with the softare > needs to be knowledgable in Python as well as in HTML. i'd like to add perhaps a different perspective. i've developed and used the following: * xmlvl (http://sf.net/projects/virgule) - it's a (non-NP-complete) XML-based programming language, which was derived from advogato's codebase. it outputs XHTML, is "template-based" and implements what is best described as an XML-based lattice-like, "crystalline" and hierarchical OO database (!!). i understood it while i was writing it, but woudldn't dare go near it, ever again. the lessons learned from this were: don't take templating to extremes (i.e. do the absolute minimum), and never ever write programming languages in XML. * python-htmltmpl (http://htmltmpl.sourceforge.net/) - it's a simple, utterly simple, HTML-syntax-like templating language, which can do "substitution", "if/else statements", and "loops". that's about it. the nice thing about htmltmpl is that it can do pre-compilation of its templates, inserting jump-points (which are used to seek() to the next precompiled statement) into the .tmplc files. this saves a _great_ deal of time and CPU cycles. the lesson from this one is hard to get across, because htmltmpl basically... works. it doesn't _need_ developing, it's complete, it works, it's never going to get up in the sourceforge "rankings" because... it does everything that it's designed to do. so it drops off of people's radar, and they reinvent the wheel. if you think you need anything more than htmltmpl, which separates out html from programming, think again. you can pass in a list of dictionaries into htmltmpl, that generates the table content, form content, whatever-content. job done. * pyjamas (http://pyjs.org) - this is treating the web page and the web browser as a desktop "canvas", i.e. turning the web browser concept on its head, and allowing you to program it in exactly the same way that you would if you were writing a desktop app with PyQt4 or PyGtk2. no kidding about, here. why on earth would you want to do something like this? it's very simple: HTML "programming" is madness. it's madness from two angles: 1) CSS abortions. as an example: i tried doing a centred-box, once. it took two weeks, and it still was a failure: worked fine in firefox, but in IE6 if you squashed the browser size, so that normally under FF you got a horizontal scrollbar, what happened in IE6 was that the content scrolled off the *top* of the screen!! unbelievable - and completely impossible to fix. 2) HTML template "option-itis" resulting in thousands of lines of HTML that becomes impossible to read, and impossible to maintain. i think the worst example i ever saw - and i'm sure people will find worse - was a technique involving _four_ separate near-identical pages (each over 3,000 lines long) - one for new entry form, one for new entry but with error-messages interspersed, one for edit, and one for edit but with error-messages interspersed. cut-and-paste gone mad. HTML templating is, for complex applications, a baaaad idea. even when you start "breaking down" the content into smaller server-side- includes, and even when you start doing multi-layered HTML templating (one template gets marked up and then substituted into another template and so on), even _that_ technique gets very quickly out-of- hand and you're left with a headache. so now i choose pyjamas over _any_ kind of web programming, any day of the week. the reason is very straightforward: the amount of code being written is small; it's in python; i can re-use classes and modules; i can even take standard python modules such as an XMLRPC client or a JSONRPC client and actually compile them (to javascript) for use... in a web browser! you can put in a < div > with an id, you can find that div using a one- line function, and you can substitute "widgets" - your classes - into that div. it's a very, very powerful technique. complex application programming should be done in a complexity-capable programming _language_. HTML, which is a markup language, is simply not designed - and was never designed - to be "programmed" or to be an NP-complete programming "language". it's great for "static content", which can be edited by graphical tools, and that's about it. so, there _is_ an alternative approach, with pyjamas, to what you're saying, diez ("Push-style ... anybody who's supposed to tinker with the softare needs to be knowledgable in Python as well as in HTML.") the alternative is: program the entire web site in pure python. as if it was a pygtk2, pyqt4 or python-wxWidgets desktop application. l. -- http://mail.python.org/mailman/listinfo/python-list
