Pledgie data parser

from django import template
from django.utils import simplejson
import urllib

register = template.Library()

class PledgieParserNode(template.Node):
    def __init__(self, var_name, pledgie_id=None, pledgie_id_var_name=None):
        self.pledgie_id = pledgie_id
        self.pledgie_id_var_name = pledgie_id_var_name
        self.var_name = var_name

    def render(self, context):
        if self.pledgie_id_var_name:
            try:
                url = "http://pledgie.com/campaigns/%d.json" % context[self.pledgie_id_var_name]
            except KeyError:
                raise template.TemplateSyntaxError, "the variable \"%s\" can't be found in the context" % self.pledgie_id_var_name
        else:
            url = "http://pledgie.com/campaigns/%d.json" % self.pledgie_id
        
        data = urllib.urlopen(url).read()
        
        context[self.var_name] = simplejson.loads(data)
        
        return ''

import re

@register.tag(name="get_pledgie_campaign_details")
def get_pledgie_campaign_details(parser, token):
    # This version uses a regular expression to parse tag contents.
    try:
        # Splitting by None == splitting by spaces.
        tag_name, arg = token.contents.split(None, 1)
    except ValueError:
        raise template.TemplateSyntaxError, "%r tag requires arguments" % token.contents.split()[0]
    
    m = re.search(r'(.*?) as (\w+)', arg)
    if not m:
        raise template.TemplateSyntaxError, "%r tag had invalid arguments" % tag_name
    pledgie_id, var_name = m.groups()
    
    if pledgie_id[0] == pledgie_id[-1] and pledgie_id[0] in ('"', "'"):
        try:
            pledgie_id = int(pledgie_id[1:-1])
        except ValueError:
            raise template.TemplateSyntaxError, "the pledgie id should be an integer..." 
        
        return PledgieParserNode(var_name, pledgie_id=pledgie_id)
    else:
        return PledgieParserNode(var_name, pledgie_id_var_name=pledgie_id)


# this also uses snippet http://www.djangosnippets.org/snippets/852/ !!

"""
{% load cache %}
{% load rss %}
{% load pledgie %}

{% cache 300 pledgie_cache %}
	{% get_pledgie_campaign_details "1174" as pledgie %}
	{{ pledgie.amount_raised }}{{ pledgie.currency }} {% if pledgie.goal %}({{ pledgie.percent_towards_goal }}%) of {{ pledgie.goal }}{{ pledgie.currency }}{% endif %} raised for {{ pledgie.title }}

	{% get_rss "http://pledgie.com/campaigns/1174/donations_feed.xml" as pledgie_rss %}
	<h1>Latest 10 donators</h1>
	<ul>
		{% for entry in pledgie_rss.entries|slice:":10" %}
		<li>{{ entry.title }}</li>
		{% endfor %}
	</ul>
{% endcache %}
"""