django philosophy: when to include templates and when to have code generate html?

Question

When using Django templates, should I have some templates that act like "subroutines", so to speak, or should I generate HTML from within my code in these cases?

For example, I have a template with several lists of names, each of which I want to turn into a select. Should I have a template that renders the name_list variable into a select, and do something like this:

#in the view:
return {'name_list_1': name_list_1, 
 'name_list_2': name_list_2, 
 'name_list_3': name_list_3}
#in the template:
{% with name_list_1 as name_list %}
 {% include "sub_name_list_select.html" %}
{% endwith %}
{% with name_list_2 as name_list %}
 {% include "sub_name_list_select.html" %}
{% endwith %}
{% with name_list_3 as name_list %}
 {% include "sub_name_list_select.html" %}
{% endwith %}

Or should I have a function in my code, name_list_to_select_html, which does the same job, and do this:

return {'name_list_1_html': name_list_to_select_html(name_list_1), 
 'name_list_2_html': name_list_to_select_html(name_list_2), 
 'name_list_3_html': name_list_to_select_html(name_list_3)}
#in the template:
{{ name_list_1_html|safe }}
{{ name_list_2_html|safe }}
{{ name_list_3_html|safe }}

Or are both of these wrong and I am getting the philosophy totally wrong?

Additional question: in terms of speed, is it slow to constantly include templates? Is that a bonus point for the in-code html generation?

• Chris Pratt: stackoverflow.com/faq#dontask. This might be more appropriate some place like codereview.stackexchange.com
• Claudiu: which particular criteria does this question fall under? it seems pretty straightforward to me: how do django developers accomplish this task?
• Chris Pratt: It's a subjective question. The bulleted list merely provides examples of common subjective questions, but if you're asking what people recommend, your question is subjective and not appropriate for StackOverflow. Like I said, the Code Review site would be okay because the entire nature of that site is to gain subjective opinions.
• Claudiu: @ChrisPratt: ah ok, i think you're right. voting to close the question.

Answer 1

Generally, HTML should only be generated in the templating system or directly related code. That keeps the view of the data completely separate from the business and functional logic. I feel that's a proper separation of concerns. Go with your first solution.

As for performance, Django should probably take around the same amount of time running either code. But it has built-in view and template fragment caching if you know those segments of code don't need to be regenerated on every request.

• Claudiu: is my first solution the commonly-accepted way to pass variables to templates, or is there something more elegant? something irks me about not being able to call a template like a function.
• Claudiu: also, due to the limited nature of django templating, i am invariably forced to have the view of the data interfere with the python code, as i have to return data structures amenable to the templating system. for example, if i want to pass a dict, it's hard to get the templating system to sort it, so i end up having to turn it into a list of items and do the sorting on the view code. isn't having the views in views.py enough separation?
• Matt S: Views gather the data to present (in an easy-to-template way), but I believe all HTML should be done directly at the template level. When I require more python functionality to write HTML, I create custom tags and filters. You also have the option of using a different templating system (although I've never tried it myself).