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templating with xhtml, xpath, and python

I've been gradually researching interesting ways to go about templating pages for Pimp 4.0 (rewrite in python). I've come to the conclusion that regexp replacement is hackish. Using a big templating toolkit is too much effort for now. However, I've come up with a solution I've yet to test thorougly, but the gist of it is:

Use an XML DOM parser to get a DOM-ified version of the webpage. Use XPath to find elements I want to modify and do so as necessary. Poof, templating. A sample template is layout.html

The following python will parse it and insert "Testing" into the content div.


import sys
from xml.dom import minidom
from xml import xpath

if __name__ == '__main__':
        foo = minidom.parse("layout.html")

        # Append a text node to the element with 'id="content"'
        div = xpath.Evaluate("//*[@id='content']", foo.documentElement)
It seems pretty simple. I'm probably going to come up with a simple-ish xml/xpath way of doing templating. We'll see how well it actually works later on, but for now it seems like a pretty simple way of doing templating. Move the complicated parts (complex xpath notions) to a templating class with an "insert text" or somesuch method and poof, simple templating. Even for complex situations where I may need to produce a table it is easy to provide a default node-tree for replicating. The particular DOM implementation I am using provides me a wonderful cloneNode() method with which to do this.

Ofcourse, if you know of any other simpler ways of doing templating in python (or in general) definitely let me know :)

xmlrpc javascript library and pimp rewrite

Yet Another Rewrite of Pimp, my music jukebox software, has commenced. This time, I'm writing it in Python. This was the best excuse I could find to learn python. I've tinkered with it before but never written an application in it.

Anyway, the interface has moved from telnet-based to web-based and uses XMLHTTPRequest (AJAX) to perform XMLRPC calls on the purely-python webserver. Python provides a wonderful standard module called 'xmlrpclib' to marshall/unmarshall XMLRPC requests and responses to/from python and XML. JavaScript, howver, lacks these marshalling features.

Some quick googling found jsolait and vcXMLRPC. Both of these are huge frameworks and are well beyond my particular needs. BOTH of them have "the suck" and fail to cleanly load into Firefox without warnings. Bah! Back at square-one. I'm left without a way to marshall xmlrpc requests and responses between javascript and xml

I spent some time learning about XMLRPC. Turns out it's a very very simple xml-based protocol for calling methods and getting results. JavaScript has DOM already so parsing XMLRPC messages is very easy.

Take a look at the 'rpcparam2hash' and 'hash2rpcparam' functions in pimp.js and see how I convert between JavaScript hashes (dictionaries) and XMLRPC messages. If I get bored I may create my own xmlrpc library specifically for making xmlrpc calls with javascript. If you want this to get done, please let me know and give me encouragement ;)

python, unicode, and pysqlite2

I have filenames I'm putting into an sqlite database. These filenames are ASCII encoded and may have upper-range characters in them. The problem, in python, is that the default encoding is UTF-8 and these ASCII upper-range characters, for whatever reason, cannot be converted. pysqlite2 provides a mechanism for fixing this problem with adapters and converters.

If you get this error:

UnicodeDecodeError: 'utf8' codec can't decode bytes in position [whatever]
Here's how I fix it (this may not be the proper solution):
from pysqlite2 import dbapi2 as sqlite

# ... several lines of code later ...

def decode_string(val):
	return val

def adapt_string(val):
	return unicode(val).encode("US-ASCII")

# ... somewhere ...

sqlite.register_adapter(str, adapt_string)
sqlite.register_converter('VARCHAR', decode_string)
I'm not certain the converter/decode is necessary, however the encoding is absolutely necessary.