Using Django built-in template tags and filters in code

In case you are wondering how to use Django's built-in template tags and filters in your source code, not inside a template here is how:

>>> from django.template.defaultfilters import *
>>> filesizeformat(1024)
u'1.0 KB'
>>> filesizeformat(1020)
u'1020 bytes'
>>> filesizeformat(102412354)
u'97.7 MB'
>>>

All built-ins live in pythonX.Y/site-packages/django/template/defaultfilters.py.