title: Parameterized reusable blocks with Jinja2 (Flask) templating engine
body: <p>In Jinja2 templating engine (using Flask), I want to achieve something like that:</p>
  
  <pre><code>{% reusable_block avatar(user) %}
       &lt;img src='{{ user.avatar }}' title='{{ user.name }}'/&gt; 
  {% reusable_block %}
  </code></pre>
  
  <p>and then in various places:</p>
  
  <pre><code>{% for u in users %}
      {% call avatar(u) %}
  {% endfor %}
  </code></pre>
  
  <p>However I can't find such a feature (I made up <code>reusable_blocks</code> for this question) in Jinja documentation.  What I need is basically reusable blocks that can take parameters. Any ideas know how can I do that with Jinja2?</p>