Question

How do you return the blob key from a blob store? and subsequently return the image URL?

Example code:

class Next(webapp.RequestHandler):
    def get(self):
        userTable_name=self.request.get('userTable_name')

        data  = db.GqlQuery("SELECT * "
                                "FROM userTable "
                                "WHERE ANCESTOR IS :1 "
                                "ORDER BY date DESC LIMIT 10",
                                userTable_key(userTable_name))

        self.response.headers['Content-Type'] = 'text/plain'


        for user in data:
            blobURL = get_serving_url(user.imageblob.key(), size=None, crop=False)
            self.response.out.write(blobURL)

I’m using a GqlQuery to return a set of Blobs (i.e. user.imageblob) and for each blob i need to determine the BlobKey. From what I can tell, “user.imageblob.key()” does not return the blobkey…?

Answer 1

Worked it out! As it turns out, I was confusing “adding an image to the datastore as a blob” vs vs adding an image to the blobstore.

a BlobReferenceProperty references an object uploaded and stored in
the blobstore while a BlobProperty stores blob data directly in the
datastore. see: How to use get_serving_url in appengine?.

Hence, get_serving_url() and user.imageblob.key() were incorrectly pointing to the datastore as opposed to the blobstore.

For examples of adding images to the blobstore see: http://code.google.com/appengine/docs/python/blobstore/overview.html