473,382 Members | 1,594 Online
Bytes | Software Development & Data Engineering Community
Post Job

Home Posts Topics Members FAQ

Join Bytes to post your question to a community of 473,382 software developers and data experts.

Using a decorator for generic html templates

Hello all,

While studying some of the templating systems available for Python,
I've come up with an idea to implement templates using decorators. The
following code snippet runs in Python 2.3; a few 2.4 only extensions
are shown as comments. Please note that I have shamelessly copied the
trim function from PEP 257, because it's needed to have the strings
properly formatted.

# HTML templating decorator
# Carlos Ribeiro
# ca********@gmail.com
# http://pythonnotes.blogspot.com

import sys

def trim(docstring):
# shamelessly taken from PEP 257:
# http://www.python.org/peps/pep-0257.html
if not docstring:
return ''
# Convert tabs to spaces (following the normal Python rules)
# and split into a list of lines:
lines = docstring.expandtabs().splitlines()
# Determine minimum indentation (first line doesn't count):
indent = sys.maxint
for line in lines[1:]:
stripped = line.lstrip()
if stripped:
indent = min(indent, len(line) - len(stripped))
# Remove indentation (first line is special):
trimmed = [lines[0].strip()]
if indent < sys.maxint:
for line in lines[1:]:
# Strip off trailing and leading blank lines:
while trimmed and not trimmed[-1]:
while trimmed and not trimmed[0]:
# Return a single string:
return '\n'.join(trimmed)

def raw_html_template(func):
Transforms a simple raw html template function into a function that
returns the __doc__ string. Non-significant spaces are removed,
making the resulting output indent correctly.
def new_func(args):
return func.__doc__

#new_func.func_name = func.func_name # 2.4 only
return new_func

class Root:
#@raw_html_template # 2.4 only
def index(self):
<h1>Hello World!</h1>

index = raw_html_template(index) #2.3 only

A simple test run is:
r = Root()
r.index() '\n <html>\n <body>\n <h1>Hello
World!</h1>\n </body>\n </html>\n '

Comments about this technique:

1) It abuses the doc string to obtain the desired effect. While some
may not like it as a hack, it's actually very clean; the resulting
code looks really nice without extra clutter.

2) More advanced decorators can be supported. For example, embedded
tags can be pre-processed by the decorator, either at "decorating
time" (when the decorator function is run) or at runtime (by means of
special code in the decorated function).

3) Methods that interleave Python code and raw HTML code are *much*
more difficult to handle. I don't have enough knowledge to deem them
impossible, but that's my best guess now. *If* someone is brave enough
to try it, my guess is that it has to rely very heavily on
introspection and low-level disassembly hacks. Not for the faint of
heart... and too [asm|C|INTERCAL]-ish for my taste :-)

4) Another approach that could be possibly taken is to use a metaclass
to control the decoration of all methods that have only docstrings and
no code. Using introspection, the constructor could check all methods
and decorate the ones that need it, building the new object

5) In real world applications, performance may be a concern. I don't
know if the decorator is applied every time a new object instance is
created, or if a caching mechanism of some type is used. If the
decorator is run everytime a new instance is about to be created, then
a different approach is needed, because many web application
frameworks rely on short lived objects to represent stuff such as
actual page handlers. That's where a metaclass approach could be more

6) Last, I don't know if the trim() function is available through some
of the standard libraries, and I have no idea upon where to look after
it. But it would be a good idea to call the standard implementation
instead of repeating the code here. (btw, the implementation has a
small bug: it leaves some extra space at the last line that should be
Carlos Ribeiro
Consultoria em Projetos
blog: http://rascunhosrotos.blogspot.com
blog: http://pythonnotes.blogspot.com
mail: ca********@gmail.com
mail: ca********@yahoo.com
Jul 18 '05 #1
0 1358

This thread has been closed and replies have been disabled. Please start a new discussion.

Similar topics

by: Ville Vainio | last post by:
It might just be that @decorator might not be all that bad. When you look at code that uses it it's not that ugly after all. A lot of the furor about this is probably because it happened so...
by: Michele Simionato | last post by:
could ildg wrote: > I think decorator is a function which return a function, is this right? > e.g. The decorator below if from http://www.python.org/peps/pep-0318.html#id1. > > def...
by: Pat Turner | last post by:
Hi, I have some XML like this: <family> <person name="bob"> <father ref="../../person" /> </person> <person name="charlie"> <child ref="../../person" />
by: Allan Bruce | last post by:
I have had a look through the FAQ and found that if I am using a class template then I need an argument list. I have tried to add this but it is not quite working - i.e. it doesnt compile. My...
by: Einar HÝst | last post by:
Hi, I'm writing a data layer for an app my company is developing. I'm thinking about wrapping up the basic data access object in two decorator objects: one to provide error checking on...
by: steve yee | last post by:
i think c should adapt c++ template standard, as well as namespace. if so, c can replace c++ in many cases.
by: nachu | last post by:
hello, 1. i would require help on how to design or how well the templates for "generic project management " can be designed the s/w used: ...
by: Tyno Gendo | last post by:
Hi I'm trying to learn patterns, which I hope to use in my PHP code, although I'm finding it hard to get any real impression of how patterns fit in properly, I've done the following test code...
by: Joe Strout | last post by:
On Nov 13, 2008, at 11:15 AM, J. Cliff Dyer wrote: Right, though the hasattr() check I put in my version of this approach takes care of that. Now THAT is something that hadn't occurred to...
by: CloudSolutions | last post by:
Introduction: For many beginners and individual users, requiring a credit card and email registration may pose a barrier when starting to use cloud servers. However, some cloud server providers now...
by: Faith0G | last post by:
I am starting a new it consulting business and it's been a while since I setup a new website. Is wordpress still the best web based software for hosting a 5 page website? The webpages will be...
by: ryjfgjl | last post by:
In our work, we often need to import Excel data into databases (such as MySQL, SQL Server, Oracle) for data analysis and processing. Usually, we use database tools like Navicat or the Excel import...
by: taylorcarr | last post by:
A Canon printer is a smart device known for being advanced, efficient, and reliable. It is designed for home, office, and hybrid workspace use and can also be used for a variety of purposes. However,...
by: Charles Arthur | last post by:
How do i turn on java script on a villaon, callus and itel keypad mobile phone
by: BarryA | last post by:
What are the essential steps and strategies outlined in the Data Structures and Algorithms (DSA) roadmap for aspiring data scientists? How can individuals effectively utilize this roadmap to progress...
by: nemocccc | last post by:
hello, everyone, I want to develop a software for my android phone for daily needs, any suggestions?
by: Sonnysonu | last post by:
This is the data of csv file 1 2 3 1 2 3 1 2 3 1 2 3 2 3 2 3 3 the lengths should be different i have to store the data by column-wise with in the specific length. suppose the i have to...
by: Hystou | last post by:
There are some requirements for setting up RAID: 1. The motherboard and BIOS support RAID configuration. 2. The motherboard has 2 or more available SATA protocol SSD/HDD slots (including MSATA, M.2...

By using Bytes.com and it's services, you agree to our Privacy Policy and Terms of Use.

To disable or enable advertisements and analytics tracking please visit the manage ads & tracking page.