How to edit Django FieldFile with S3 storage backend

Question

I have the S3 storage backend set up and I am able to upload files to the S3 bucket. I am using the boto and django-storages modules. The config in settings.py looks like this:

AWS_STORAGE_BUCKET_NAME = 'xxxxx'
AWS_ACCESS_KEY_ID = 'xxxxxxxxxxxxx'
AWS_SECRET_ACCESS_KEY = 'xxxxxxxxxxxxxxxxxxxxxxxxxx'

AWS_S3_CUSTOM_DOMAIN = '%s.s3.amazonaws.com' % AWS_STORAGE_BUCKET_NAME

STATICFILES_LOCATION = 'static'
STATICFILES_STORAGE = 'custom_storages.StaticStorage'
STATIC_URL = "https://%s/%s/" % (AWS_S3_CUSTOM_DOMAIN, STATICFILES_LOCATION)

MEDIAFILES_LOCATION = 'media'
MEDIA_URL = "https://%s/%s/" % (AWS_S3_CUSTOM_DOMAIN, MEDIAFILES_LOCATION)
DEFAULT_FILE_STORAGE = 'custom_storages.MediaStorage'

and the class in models.py:

class Model (models.Model):
    name            = models.CharField(max_length=50, null=False, blank=False)
    file            = models.FileField(upload_to='models/%Y/%m/%d/')

What I need is modify the file with an external program, which was possible with the default storage backend (using local disk) followingly:

def modify_model(model):
    try:
        subprocess.check_call(["/usr/bin/program", model.file.path])
    except:
        pass

As the S3 backend does not support the path attribute, I am wondering how should I do it correctly? The error looks like this:

>>> m.file.path
Traceback (most recent call last):
  File "", line 1, in 
  File ".../site-packages/django/db/models/fields/files.py", line 64, in _get_path
return self.storage.path(self.name)
  File ".../site-packages/django/core/files/storage.py", line 111, in path
    raise NotImplementedError("This backend doesn't support absolute paths.")
NotImplementedError: This backend doesn't support absolute paths.

My first thoughts are saving the file locally, modifying it and then uploading the modified version.

>>> f = open('localfile', 'wb')
>>> m = Model.objects.first()
>>> f.write(m.file.read())
1503
>>> f.close()
>>> # modify the file here
>>> f = open('localfile', 'rb')
>>> m.file.save(os.path.basename(m.file.name), File(f))

This works as intended, BUT - Is there a way to work with the Django FieldFile class natively (with the S3 backend) to modify the files without creating the temporary ones?

How to edit Django FieldFile with S3 storage backend

0 Answers