webapp2 sessions with the blobstore

I recently started using webapp2 sessions, and was happy with how they work. However, when trying to access sessions during an upload to the blobstore, I was not able to since the BlobstoreUploadHandler did not inherit from the new BaseHandler I created as directed by the webapp2 session instructions. I wanted to do this to send a message to the user that their upload was successful, using the add_flash() function. Appending ?message=Upload successful. to the redirect URL would have worked, but is lame.

Trying to use it through multiple inheritance also fails: class EntryUploadHandler(blobstore_handlers.BlobstoreUploadHandler, BaseUploadHandler): with some error.

The solution was to create a BaseUploadHandler class with special handling for sessions. It appears that the upload handler doesn’t act the same as a normal RequestHandler, so you have to do everything in one place: class BaseUploadHandler(blobstore_handlers.BlobstoreUploadHandler): def add_message(self, level, message): store = sessions.get_store(request=self.request) session = store.get_session() session.add_flash(message, level, BaseHandler.MESSAGE_KEY) store.save_sessions(self.response)

Full code here.