HTML generation vs PSP vs Templating Engines

[has]

pkassianidis at gmail.com wrote:

> Could someone that has used all the different ways mentioned above for
> dynamic HTML
> content, suggest what the pros and cons of the different methods are?

Not used them all - as you say, there's a plethora of options - but to
give you a general idea of the territory...

First choice you have is between HTML generators vs. HTML templating
systems:

- HTML generators create all markup from scratch. Useful when producing
arbitrary markup/layout whose entire structure must be determined
programmatically, e.g. applying paragraph and character styling to a
big chunk of text, creating arbitrary HTML form layouts based on other
input. Examples: htmlgen (crusty, HTML 3.1-era), Nevow's Stan engine.

- HTML templates insert individual items of data into a mostly static
block of HTML markup written in advance by e.g. a graphic designer.
Useful when creating documents that are fairly regular in structure -
most fall into this category - as it's much easier to create the
repetitious parts using standard HTML editing tools than write code to
produce it all programmatically.

Sometimes you might combine the two methods, using an HTML generator to
create sections of markup from arbitrary input which is then inserted
into a full-page template to produce the finished HTML document.


Assuming a templating-based solution is the appropriate choice for you
(which it most likely is), there are three general approaches to choose
from:

1. Systems that embed markup in code. This is a fairly small category.
It's fairly programmer-friendly since you've direct access to all
language features, but hostile to web designers as you have to pull
your HTML markup apart and insert it into program code to produce the
final template, making it a pain to modify that markup later. Examples:
ad-hoc solutions using Python's string interpolation, the Quixote
framework's built-in templating support, Karrigell (though it supports
some aspects of approach 2 as well).

2. Systems that embed code in markup. This is the most common category
with a fair amount of variety and capabilities to choose from. Lots of
obviously PHP/ASP-inspired designs. Two sub-categories: systems that
embed standard Python code, e.g. PSP, and systems that embed a custom
language, e.g. Cheetah. Some provide no restrictions on what you can
get up to within embedded code, others restrict functionality to
enforce a strict separation between presentation logic and model logic.
Embedding styles also vary: some mix code statements and markup
directly (e.g. Cheetah), some embed code statements in special <%...%>
style tags (e.g. PSP), some hide all code within HTML tag attributes
(e.g. TAL, Kid), providing varying degrees of designer-friendliness as
a result.

3. DOM-style systems. This is a more recent arrival and a smaller
category. These systems completely separate markup from presentation
logic. Selected HTML elements are flagged using specific named tag
attributes (e.g. id="somename") or simple compiler directives, e.g.
(nevow:render="somename"); the template is then compiled into a simple
templating-oriented (i.e. not w3c) DOM, allowing these elements to be
manipulated programmatically by standard Python scripts. Very designer
and developer friendly, although less experienced programmers may find
the higher level of abstraction involved a bit offputting. Examples:
PyMeld, HTMLTemplate [1], Nevow.Render.


For a fairly extensive list of available systems, see
<http://wiki.python.org/moin/WebProgramming>. Unfortunately they're not
well categorised there, but I can't think of a better, up-to-date list
off the top of my head and most will provide decent overviews so it
shouldn't take too long to take a quick look at each.

Note that some templating engines are embedded into larger web
programming frameworks and may or may not be usable independently.
Conversely, some web frameworks may be coupled to a specific templating
system, while others allow you to choose your own.

HTH

has

--
[1] Disclaimer: I wrote HTMLTemplate. Also, shameless plug:
<http://freespace.virgin.net/hamish.sanderson/htmltemplate.html>