filters.py

# nope

nav.html

{% macro nav_link(endpoint, name) %}
 {%- if endpoint == request.endpoint -%}
    <li class="active">
        <a href="{{ url_for(endpoint) }}">{{ name }}</a>
    </li>
 {%- else -%}
    <li>
        <a href="{{ url_for(endpoint) }}">{{ name }}</a>
    </li>
 {%- endif -%}
{% endmacro %}
<ul class="nav nav-tabs">
    {{ nav_link("index", "home") }}
    {{ nav_link("dashboard", "dashboard") }}
    {{ nav_link("trends", "trending") }}
</ul>