Django snippets

def do_ifinlist(parser, token, negate):
    bits = list(token.split_contents())
    if len(bits) != 3:
        raise TemplateSyntaxError, "%r takes two arguments" % bits[0]
    end_tag = 'end' + bits[0]
    nodelist_true = parser.parse(('else', end_tag))
    token = parser.next_token()
    if token.contents == 'else':
        nodelist_false = parser.parse((end_tag,))
        parser.delete_first_token()
    else:
        nodelist_false = NodeList()
    return IfInListNode(bits[1], bits[2], nodelist_true, nodelist_false, negate)

def ifinlist(parser, token):
    """
    Given an item and a list, check if the item is in the list

    -----
    item = 'a'
    list = [1, 'b', 'a', 4]
    -----
    {% ifinlist item list %}
        Yup, it's in the list
    {% else %}
        Nope, it's not in the list
    {% endifinlist %}
    """
    return do_ifinlist(parser, token, False)
ifinlist = register.tag(ifinlist)

class IfInListNode(Node):
    def __init__(self, var1, var2, nodelist_true, nodelist_false, negate):
        self.var1, self.var2 = var1, var2
        self.nodelist_true, self.nodelist_false = nodelist_true, nodelist_false
        self.negate = negate

    def __repr__(self):
        return "<IfInListNode>"

    def render(self, context):
        try:
            val1 = resolve_variable(self.var1, context)
        except VariableDoesNotExist:
            val1 = None
        try:
            val2 = resolve_variable(self.var2, context)
        except VariableDoesNotExist:
            val2 = None
        if val1 in val2:
            return self.nodelist_true.render(context)
        else:
            return self.nodelist_false.render(context)