Some helpful handlers for downloading blobs.

views.py

class BlobMigrationHandler(YourCustomHandler):
    " List out the blob keys so we can migrate them. "
    
    def get(self):
        
        CHUNK = 300
        cursor = self.request.GET.get('cursor')
        
        q = blobstore.BlobInfo.all()
        
        if cursor:
            q.with_cursor(cursor)
            
        data = {
                'blobkeys': [dict(key=str(x.key())) for x in q.fetch(CHUNK)],
                'cursor':str(q.cursor())
        }

        self.respond_json(data)
        
        
class BlobDownloadHandler(blobstore_handlers.BlobstoreDownloadHandler):
    " Dumb download handler.  Only using for migration. "
    
    def get(self, resource):
        resource = str(urllib.unquote(resource))
        blob_info = blobstore.BlobInfo.get(resource)
        self.send_blob(blob_info)