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Editorial Team
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Asked: 2026-06-02T16:11:26+00:00

I’ve saved a document in the blobstore, and am trying to retrieve it within

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I’ve saved a document in the blobstore, and am trying to retrieve it within a handler (which handles a task). I’ve had a read of the appengine documentation regarding the how to use blobstore, but am struggling to get it to work for my case. I’ve tried the following within the handler but cannot seem to have the object returned as the saved file (e.g. .pdf or .txt)

class SendDocuments(webapp2.RequestHandler):
    def post(self):
        document_key = self.request.get("document_key")
        document_key = Key(str(document_key))
        the_document = DocumentsModel.all().filter("__key__ =", document_key).get()
        file_data = blobstore.BlobInfo.get(str(the_document.blobstore_key)) # returns a blobinfo object
        file_data.open() # returns a blobreader object
        file_data.open().read() # returns a string

I’ve also tried

class ServeSavedDocument(blobstore_handlers.BlobstoreDownloadHandler):
  def get(self, blob_key):
    self.send_blob(blob_key, save_as=True)
    return

class SendDocuments(webapp2.RequestHandler):
    def post(self):
        document_key = self.request.get("document_key")
        document_key = Key(str(document_key))
        the_document = DocumentsModel.all().filter("__key__ =", document_key).get()
        grab_blob = ServeSavedDocument()
        file_data = grab_blob.get(self, str(the_document.blobstore_key))

But the call to ServeSavedDocument fails with 

'NoneType' object has no attribute 'headers'

I’ve had a look at the files api but the only example that’s not saving the file simply seems to return the blob key i.e.

blob_key = files.blobstore.get_blob_key(file_name)

What is the best way to grab a saved file in the blobstore from within a handler?

EDIT 1:

I’m trying to retrieve the txt file or pdf file from the blobstore in a format / state that can be encoded as a file in a post request using the following code

from google.appengine.api import urlfetch
from poster.encode import multipart_encode
# assuming here that file_data is the file object
payload = {}
payload['user_id'] = '1234123412341234'
payload['test_file'] = MultipartParam('test_file', filename=file_data.filename,
                                      filetype=file_data.type,
                                      fileobj=file_data.file)
data,headers= multipart_encode(payload)
send_url = "http://127.0.0.0/"
t = urlfetch.fetch(url=send_url, payload="".join(data), method=urlfetch.POST, headers=headers)
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1 Answer

  1. Editorial Team

    Okay, after a lot of messing around I”ve found that this works! The key was to simply call open() on the blobinfo object.

    class SendDocuments(webapp2.RequestHandler):
    def post(self):
        document_key = self.request.get("document_key")
        document_key = Key(str(document_key))
        the_document = DocumentsModel.all().filter("__key__ =", document_key).get()
        file_data = blobstore.BlobInfo.get(str(the_document.blobstore_key))
        payload = {}
        payload['user_id'] = '1234123412341234'
        payload['test_file'] = MultipartParam('the_file', filename="something",
                                      filetype=file_data.content_type,
                                      fileobj=file_data.open())
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