# The file reference must be populated with a django.core.files.File instance
# but File cannot handle file-like objects such as those returned by urlopen -
# see http://code.djangoproject.com/ticket/8501
#
# Since we'd like to get the normal file name collision avoidance, automatic
# location handling, etc. we'll create a django NamedTemporaryFile because the
# default file storage save logic is smart enough to simply move the temporary
# file to the correct location.
 
from django.core.files import File
from django.core.files.temp import NamedTemporaryFile

img_temp = NamedTemporaryFile(delete=True)
img_temp.write(urllib2.urlopen(url).read())
img_temp.flush()

im.file.save(img_filename, File(img_temp))