Python-сообщество

class FilesCategory(models.Model):
    name = models.CharField(max_length=255)
class File(models.Model):
    name = models.CharField(max_length=255)
    file = models.FileField(upload_to=get_file_path)
    category = models.ForeignKey(FilesCategory, related_name='files')
    group = models.ForeignKey(Group)

group = Group.objects.get(id=group_id)
f = File.objects.filter(group = group)

{% for c in categories %}
    <li>{{ c.name }}
        <ul style="margin-left: 20px;">
        {% for file in c.files.all %}
            <li>{{ file.name }}</li>
        {% endfor %}
        </ul>
    </li>
{% endfor %}

res = dict()
for f in File.objects.all():
   res.setdefault(f.group, []).append(f)