这个密码对我有效。
class DownloadHandler(blobstore_handlers.BlobstoreDownloadHandler):
def get(self):
filename = self.request.get('file_name')
key1 = functions.getFileList(filename)
blob_info = blobstore.BlobInfo.get(blobstore.BlobKey(str(key1.blob)))
self.send_blob(blob_info,save_as=True)
感谢@Dustin Ingram