Template tag: Group variables into list

import re
from django import template
register = template.Library()

class GroupNode(template.Node):
    def __init__(self, group_variables, var_name):
        self.group_variables = list()
        for group_variable in group_variables:
            self.group_variables += [template.Variable(group_variable)]
        self.var_name = var_name
    def render(self, context):
        try:
            group = list()
            for variable in self.group_variables:
                group += [variable.resolve(context)]
            context[self.var_name] = group
            return ''
        except template.VariableDoesNotExist:
            return ''

@register.tag
def group(parser, token):
    '''Groups an arbitrary number of variables into a list.
    
    ex: {% group "foo", 2, "bar" as my_list %}
    '''
    try:
        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
    group_string, var_name = m.groups()
    group = [g.strip() for g in group_string.split(',')]
    return GroupNode(group, var_name)