Question

I want to create a process using GAE by which, given a url, a file is downloaded and stored as a blob in the blobstore. Once this is done I want to pass this blob along as POST data to a second url. However for this second part to work I need to be able to open the blob as a file instance.

I’ve figured out how to do the first part

from __future__ import with_statement
from google.appengine.api import files

imagefile = urllib2.urlopen('fileurl')
# Create the file
file_name = files.blobstore.create(mime_type=imagefile.headers['Content-Type'])
# Open the file and write to it
with files.open(file_name, 'ab') as f:
    f.write(imagefile.read())
# Finalize the file. Do this before attempting to read it.
files.finalize(file_name)
# Get the file's blob key
blob_key = files.blobstore.get_blob_key(file_name)

But I can’t figure out how to do the second part. So far I’ve tried

1. ffile = files.open(files.blobstore.get_file_name(blob_key), 'r')

2. from google.appengine.ext import blobstore

   ffile = blobstore.BlobReader(blob_key)
   

3. from google.appengine.ext import blobstore

   ffile = blobstore.BlobInfo.open(blobstore.BlobInfo(blob_key))
   

All of which gives Falsefor isinstance(ffile, file).

Any help is appreciated.

Answer 1

ffile = blobstore.BlobReader(blob_key) works. However, the returned object has only a file-like interface; it dosn’t extend a file-class. Therefore, the isinstance test wont work. Try something like if ffile and "read" in dir( ffile ).