Django File mixin to automatically folderize uploaded file by app label and ID

models.py

from django.db import models


class FileAppIdFolderMixin(models.Model):
    def upload_to(self, filename):

        return '{app}/{id}/{filename}'.format(
            app=self._meta.app_label,
            id=self.id,
            filename=filename
        )

    file = models.FileField(
        upload_to=upload_to,
        blank=True
    )

    class Meta:
        abstract = True