How to avoid NotImplementedError "Only tempfile.TemporaryFile is available for use" in django on Google App Engine?

Question

I'm using Django 1.1 on Google App Engine through use_library. No Django GAE helper, Django non-rel or similar tools are used here. Django handles URLs routing, forms validation etc., but I'm using pure App Engine models.

In one of my Django forms there is a FileField, which from time to time, seems to call django.core.files.uploadedfile.TemporaryUploadedFile. This class then uses tempfile.NamedTemporaryFile and this results in App Engine raising:

File "/base/python_runtime/python_dist/lib/python2.5/tempfile.py", line 45, in PlaceHolder
   raise NotImplementedError("Only tempfile.TemporaryFile is available for use")

Trying to solve this problem I took uploadedfile module from Google App Engine Helper for Django (which doesn't use NamedTemporaryFile) saved it as gae_uploadedfile.py in application directory and in my _djangomain.py_ file I added:

from google.appengine.dist import use_library
use_library('django', '1.1')
(...)
import gae_uploadedfile
django.core.files.uploadedfile = gae_uploadedfile

djangomain.py is a file where i redirect all urls - in app.yaml I have:

- url: /.*
  script: djangomain.py

But it didn't help, I still get this exception. What am I doing wrong, is there other solution to avoid this error while using FileField from django.forms?

Answer 1

You need to update the settings.py file with the following to change the default Django behaviour:

# only use the memory file uploader, do not use the file system - not able to do so on
# google app engine
FILE_UPLOAD_HANDLERS = ('django.core.files.uploadhandler.MemoryFileUploadHandler',)
FILE_UPLOAD_MAX_MEMORY_SIZE = 2621440 # the django default: 2.5MB

More info here:FILE_UPLOAD_MAX_MEMORY_SIZE and upload-handlers

If you are uploading images you will be restricted by the 1MB quotas for image transformation etc.. Quotas_and_Limits