Useful django template tags and filters

django-template-filters.py

# coding: utf-8
import json

from django import template
from django.utils.dateparse import parse_datetime
from django.utils.html import mark_safe


register = template.Library()


@register.filter
def get_range(value, start_from=0):
    """
    Filter - returns a list containing range made from given value
    Usage (in template):

    <ul>{% for i in 3|get_range %}
        <li>{{ i }}. Do something</li>
    {% endfor %}</ul>

    Results with the HTML:
    <ul>
        <li>0. Do something</li>
        <li>1. Do something</li>
        <li>2. Do something</li>
    </ul>

    Instead of 3 one may use the variable set in the views
    """

    return range(start_from, value)


@register.filter('parse_datetime')
def parse_datetime_filter(date_string):
    """
    Return a datetime corresponding to date_string, parsed according to DATETIME_INPUT_FORMATS
    For example, to re-display a date string in another format::
    {{ "01/01/1970"|parse_datetime|date:"F jS, Y" }}

    """

    try:
        return parse_datetime(date_string)
    except Exception:
        return date_string


@register.filter
def toJSON(value):
    return mark_safe(json.dumps(value))


@register.filter
def addcss(field, arg):
    """
        Add class to field in templates

        {{ field|addcss:'my-class' }}
    """

    return field.as_widget(attrs={'class': arg})

django-template-tags.py

# coding: utf-8

from django import template
from django.conf import settings
from django.contrib.staticfiles.storage import staticfiles_storage
from django.template import Node

register = template.Library()


@register.simple_tag
def settings_value(name):
    return getattr(settings, name, "")


@register.simple_tag
def javascript(filename, type='text/javascript'):
    """A simple shortcut to render a ``script`` tag to a static javascript file"""
    if '?' in filename and len(filename.split('?')) is 2:
        filename, params = filename.split('?')
        return '<script type="%s" src="%s?%s"></script>' % (type, staticfiles_storage.url(filename), params)
    else:
        return '<script type="%s" src="%s"></script>' % (type, staticfiles_storage.url(filename))


@register.simple_tag
def js(filename, type='text/javascript'):
    """A simple shortcut"""
    return javascript(filename, type=type)


@register.simple_tag
def css(filename):
    """A simple shortcut to render a ``link`` tag to a static CSS file"""
    return '<link rel="stylesheet" type="text/css" href="%s" />' % staticfiles_storage.url(filename)


@register.simple_tag
def app_css(app_name, file_path, *args, **kwargs):
    """
    A simple shortcut to render a ``link`` tag to a django app related css file
    {% app_css 'customer' 'edit-page.css' %}
    """

    path = '{version}/{app_name}/css/{file_path}'.format(
        version=settings.TEMPLATE_NAME,
        app_name=app_name,
        file_path=file_path
    )

    return css(path)


@register.simple_tag
def app_js(app_name, file_path, *args, **kwargs):
    """
    A simple shortcut to render a ``script`` tag to a django app related js file
    {% app_js 'customer' 'edit-page.js' %}
    """

    path = '{version}/{app_name}/js/{file_path}'.format(
        version=settings.TEMPLATE_NAME,
        app_name=app_name,
        file_path=file_path
    )

    return js(path)


# http://kuttler.eu/code/django-almost-spaceless-template-tag/
class AlmostSpacelessNode(Node):
    def __init__(self, nodelist):
        self.nodelist = nodelist

    def render(self, context):
        return self.remove_whitespace(self.nodelist.render(context).strip())

    def remove_whitespace(self, value):
        value = re.sub(r'\n', ' ', value)
        value = re.sub(r'\s+', ' ', value)
        return value


@register.tag(name='almostspaceless')
def spaceless(parser, token):
    """
    Remove all whitespace except for one space from content
    """
    nodelist = parser.parse(('endalmostspaceless',))
    parser.delete_first_token()
    return AlmostSpacelessNode(nodelist)