python - Transferring Blob_values to a queue

I have trouble transferring the blob_name to my queue so I can read out the information there and process it. The information or content of the Blob is basically just a list of text (CSV). I also tried this with the blob_key, but both result in the same error.

# I create the blob - works fine, checked in Dashboard
file_name = files.blobstore.create(mime_type='text/comma-separated-values',_blobinfo_uploaded_filename=str(datetime.now()))
with files.open(file_name, 'a') as f:
f.write(low)
files.finalize(file_name)
# Transferring the variables to the queue
taskqueue.add(url='/filtering_brands', params={'filter_name' : filter_name, 'user' : user, 'lowkey' : file_name})
self.redirect('/?sent=True')
class Queue(webapp2.RequestHandler):
def post(self):
# Requesting the variables
filter_name = self.request.get('filter_name')
user = self.request.get('user')
lowkey = self.request.get('lowkey')
blob_key = files.blobstore.get_blob_key(lowkey)
# This is (apparently) the part that doesn't work
low = blobstore.BlobReader(blob_key)
# Process the data and transfer it to an email script

This is the error I am receiving:

TypeError: object of type 'BlobReader' has no len()