Django-templates: Why doesn't {% if "string"|length > 10 %} work at all?

Question

I'm using Django 1.3. If I put the following fragment into my template:

{% if 'my string'|length > 10 %}{{ 'my string'|length }}{% endif %}

the rendering engine prints '9'. The only thing I can think of is that the |length filter is returning a string, but that seems odd in the extreme. Can anyone point me in the right direction?

Thanks!

Edit:

The length I actually want to test comes from flatpage.title provided by django.contrib.flatpages. For this reason, I'd rather not hack the view to provide the information I need to the template. I'd hoped I could simply use the |length filter as described in the Django docs, here. However, as has been pointed out, the only way to do this seems to be to also use the |get_digit filter, whose behaviour is not clearly defined in this respect. :(

Answer 1

I'm recommending not using this but I have combined the get_digit and the length filters before to make this work.

{% if "12345678901234567890"|length|get_digit:"-1" > 20 %} 
    {{ "12345678901234567890"|length }} 
{% endif %}

results in nothing in the template, but:

{% if "12345678901234567890"|length|get_digit:"-1" > 19 %} 
    {{ "12345678901234567890"|length }} 
{% endif %}

results in:

20

being printed.

Answer 2

Yes, filters always return a string.

You can achive the desired functionality by calculating string length in a view and do something like this:

{% if str_length > 10 %}
    {{ str_length }}
{% endif %}

Or create a custom filter for your needs: http://code.djangoproject.com/wiki/BasicComparisonFilters

Edited for typo