class UploadRankingHandler(webapp.RequestHandler):

    def post(self):
        fish_image_file = self.request.get('file')
file_name = files.blobstore.create(mime_type='image/png',
    _blobinfo_uploaded_filename='testfilename.png')
file_str_list = splitCount(fish_image_file, 65520)
with files.open(file_name, 'a') as f:
    for line in file_str_list:
        f.write(line)
How to write Big files into Blobstore using experimental API?