CODEWITHSUNDEEP
pythongoogle-app-engineblobstore
Lokal_Profil
Lokal_Profil

Reputation: 394

Handling a blobstore blob as a file (python)

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.

Upvotes: 2

Views: 1836

Answers (2)

voscausa
voscausa

Reputation: 11706

To read file_data from the blobstore :

blob_key = .....                                        # is what you have
file_name = blobstore.BlobInfo.get(blob_key).filename   # the name of the file (image) to send 
blob_reader = blobstore.BlobReader(blob_key)
file_data = blob_reader.read()                          # and the file data with the image

But you can also send an url with the blob_key and serve the url. And for images you do not have to serve the images yourself, because you can post a get_serving_url, making use of the Google High Perfomance Image Serving API with dynamic scaling. Serving images this way is also very cheap.

Here is an example of such an url :

https://lh6.ggpht.com/lOghqU2JrYk8M-Aoio8WjMM6mstgZcTP0VzJk79HteVLhnwZy0kqbgVGQZYP8YsoqVNzsu0EBysX16qMJe7H2BsOAr4j=s70

Upvotes: 1

T. Steinrücken
T. Steinrücken

Reputation: 469

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 ).

Upvotes: 2

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