Django model mixin class to extends django-storages (https://github.com/jschneier/django-storages) ability to backup media files to local storage.

mixins.py

import os

from django.conf import settings
from django.core.files import File
from django.core.files.storage import FileSystemStorage


class LocalMediaSaveMixin(object):
    """Mixin class to for backing up media files on model that has
    image/file fields. To use it, ensure to keep in my python multiple
    inheritance order. The top most hierarchy must be on the most right.

    example:

        class MyModel(LocalMediaSaveMixin, models.Model):
            pass
    """

    def __init__(self, *args, **kwargs):
        super(LocalMediaSaveMixin, self).__init__(*args, **kwargs)
        # Setup django local file system storage.
        self.storage               = FileSystemStorage()
        self.storage.base_location = settings.MEDIA_ROOT
        self.media_fields          = [
            i for i in self._meta.fields
            if i.__class__.__name__ in ['ImageField', 'FileField']
        ]

    def save(self, *args, **kwargs):
        """Save media file (Image, File) to local storage."""
        from product.models import file_path  # This import was from function that use to define path location and used on `upload_to=`
        super(LocalMediaSaveMixin, self).save(*args, **kwargs)
        # Getting file or image fields.
        for field in self.media_fields:
            raw_file    = getattr(self, field.name)
            file_name   = os.path.split(raw_file.name)[1]
            django_file = File(raw_file, file_name)
            root, _     = os.path.split(file_path(None, file_name))
            root        = root.replace('static/', '')
            # Ensure the file is not exists.
            if not os.path.isfile(os.path.join(settings.MEDIA_ROOT, root, file_name)):
                self.storage.location = os.path.join(settings.MEDIA_ROOT, root)
                self.storage.save(file_name, django_file)

    @property
    def local_media(self):
        """Listed all local media directory."""
        media = {}
        for i in self.media_fields:
            raw_file      = getattr(self, i.name)
            media[i.name] = os.path.join(settings.MEDIA_ROOT, raw_file.name.replace('static/', ''))
        return media