bad_views.py

@view_config(renderer='myapp:templates/blog_detail.j2')
@has_tag_cloud  # ug, but I need that tag_cloud!
def blog_detail(request, blog_slug):
    blog = fetch_blog(blog_slug)
    return {}


@view_config(renderer='myapp:templates/tag_cloud.j2')
@has_tag_cloud  # silly, since this *is* the tag cloud...
def tag_cloud(request, blog_slug):
    # imagine this method is called via ajax a lot,
    # to make the tag cloud spin or change or something...
    return {}


def has_tag_cloud(function):
    @wraps(function)
    def wrapper(request, *args, **kwargs):
            cloud = fetch_tag_cloud(blog_slug)
            ret = function(request, *args, **kwargs)
            ret['tag_cloud'] = cloud
            return ret

blog_detail.html

{% extends "layouts/base.j2" %}

{% block content %}
<h1>{{ blog.title }}</h1>
{{ blog.html }}
{% endblock %}


{% block callouts %}
{{ super() }}

{# ajax or not, we can insert the tag_cloud into the DOM here: #}
{% view 'tag_cloud' %}

{% endblock %}

good_views.py

@view_config(renderer='myapp:templates/blog_detail.j2')
def blog_detail(request, blog_slug):
    blog = fetch_blog(blog_slug)
    return {}


@view_config(renderer='myapp:templates/tag_cloud.j2')
def tag_cloud(request, blog_slug):
    # could be an ajax request, either way...
    cloud = fetch_tag_cloud(blog_slug)
    return {'tag_cloud': cloud}