Simple django template filters to add attributes to Django form fields

template_filters.py

from django import template
register = template.Library()

@register.simple_tag()
def render(field, attrs, val=None):
    """
    Renders a form field as a widget with the attributes you specify (separated by commas)
    Example usage: {% render field 'class="form-control is-invalid", required' field.value %}
    """
    for attr in attrs.split(', '):
        x = attr.split('=')
        try:
            field.field.widget.attrs[x[0]] = x[1].strip('\"')
        except IndexError:
            field.field.widget.attrs[x[0]] = True
        if val is not None:
            field.field.widget.attrs['value'] = val
    return field.as_widget()

@register.filter()
def add_class(field, classname):
    """
    Adds a class to a form field
    Example usage: {{ form.field|add_class:'form-control' }}
    """
    try:
        field.field.widget.attrs['class'] += ' %s' % classname
    except KeyError:
        field.field.widget.attrs['class'] = classname
    return field.as_widget()