App Engine Photo Upload (with BlobStore)

models.py

from __future__ import with_statement
from google.appengine.ext import db, blobstore
from google.appengine.api import memcache, files, images

class Photo(db.Model):
  created         = db.DateTimeProperty(auto_now_add=True)
  updated         = db.DateTimeProperty(auto_now=True)
  blob_key        = blobstore.BlobReferenceProperty()
  url             = db.StringProperty()
  thumbnail_url   = db.StringProperty()

  def upload_blob(self, file):
    file_name = files.blobstore.create(mime_type='image/png')
    with files.open(file_name, 'a') as f:
      f.write(file)
    files.finalize(file_name)
    self.blob_key = files.blobstore.get_blob_key(file_name)
    self.url = images.get_serving_url(self.blob_key)
    self.thumbnail_url = images.get_serving_url(self.blob_key, size=100, crop=True)