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Editorial Team
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Asked: 2026-05-24T23:31:41+00:00

How can i add pass Model-Specific urls to the Template. Let’s say, i want

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How can i add pass Model-Specific urls to the Template.
Let’s say, i want to build an edit-link.
I would guess, using the uri_for() function would be an easy approach.

But the following gives me “UndefinedError: ‘webapp2’ is undefined”

{% webapp2.uri_for("editGreeting", greeting.key().id()) %}

Or should i prepare these in the MainPage-Request-Handler?
If so, i don’t know how to add them to each greeting.

The following Code-Example is taken from:
http://webapp-improved.appspot.com/tutorials/gettingstarted/templates.html

Controller/Handler

class MainPage(webapp2.RequestHandler):
    def get(self):
        guestbook_name=self.request.get('guestbook_name')
        greetings_query = Greeting.all().ancestor(
            guestbook_key(guestbook_name)).order('-date')
        greetings = greetings_query.fetch(10)

        if users.get_current_user():
            url = users.create_logout_url(self.request.uri)
            url_linktext = 'Logout'
        else:
            url = users.create_login_url(self.request.uri)
            url_linktext = 'Login'

        template_values = {
            'greetings': greetings,
            'url': url,
            'url_linktext': url_linktext,
        }

        path = os.path.join(os.path.dirname(__file__), 'index.html')
        self.response.out.write(template.render(path, template_values))

Template/View:

<html>
  <body>
    {% for greeting in greetings %}
      {% if greeting.author %}
        <b>{{ greeting.author.nickname }}</b> wrote:
      {% else %}
        An anonymous person wrote:
      {% endif %}
      <blockquote>{{ greeting.content|escape }}</blockquote>
    {% endfor %}

    <form action="/sign" method="post">
      <div><textarea name="content" rows="3" cols="60"></textarea></div>
      <div><input type="submit" value="Sign Guestbook"></div>
    </form>

    <a href="{{ url }}">{{ url_linktext }}</a>
  </body>
</html

The class BaseHandler is the class all handlers inherit from.
I tried the following as @moraes suggested.
I still get: 

value = self.func(obj)
File "C:\Users\timme04\python\hellowebapp\handlers\basehandler.py", line 23, in jinja2
return jinja2.get_jinja2(factory=self.jinja2_factory)
File "C:\Users\timme04\python\hellowebapp\webapp2_extras\jinja2.py", line 212, in get_jinja2
jinja2 = app.registry[key] = factory(app)
TypeError: jinja2_factory() takes exactly 1 argument (2 given)

🙁

import webapp2

from webapp2_extras import jinja2

class BaseHandler(webapp2.RequestHandler):

    def jinja2_factory(app):
        j = jinja2.Jinja2(app)
        j.environment.filters.update({
            # Set filters.
            # ...
        })
        j.environment.globals.update({
            # Set global variables.
            'uri_for': webapp2.uri_for,
            # ...
        })
        return j

    @webapp2.cached_property
    def jinja2(self):
        # Returns a Jinja2 renderer cached in the app registry.
        return jinja2.get_jinja2(factory=self.jinja2_factory)

    def render_response(self, _template, **context):
        # Renders a template and writes the result to the response.
        rv = self.jinja2.render_template(_template, **context)
        self.response.write(rv)
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1 Answer

  1. Editorial Team

    You must set uri_for as a global variable. One way to do it is to set an initializer for global variables and filters:

    import webapp2
from webapp2_extras import jinja2

def jinja2_factory(app):
    j = jinja2.Jinja2(app)
    j.environment.filters.update({
        # Set filters.
        # ...
    })
    j.environment.globals.update({
        # Set global variables.
        'uri_for': webapp2.uri_for,
        # ...
    })
    return j

class BaseHandler(webapp2.RequestHandler):

    @webapp2.cached_property
    def jinja2(self):
        # Returns a Jinja2 renderer cached in the app registry.
        return jinja2.get_jinja2(factory=jinja2_factory)

    def render_response(self, _template, **context):
        # Renders a template and writes the result to the response.
        rv = self.jinja2.render_template(_template, **context)
        self.response.write(rv)

    Edit: changed example to use a RequestHandler.

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