Ever find yourself wishing for the modulo operator (%) in Django templates? I did. Its easy enough to create your own custom filter so why not do it?

Caveat: I couldn't figure out how to get the filter to accept two arguments to do the modulo test against so I defaulted the test value to zero. If there is a way to add a second argument I would love to add that to the code.

In the templatetags directory of your Django install, add a file named 'mod.py'. In that file add the following code:

from django import template
register = template.Library()

def mod(value, arg):
    if value % arg == 0:
        return True
    else:
        return False

register.filter('mod', mod)


In your template use the mod filter like this:

...
{% load mod %}
...
<tr bgcolor="{% if forloop.counter|mod:2 %}#cccccc{% else %}#ffffff">
...

This will alternate every other row's background color between gray and white.

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