Downloading a file on the fly from Flask+sqlalchemy

Following code snippet shows how to implement downloading a file with flask.

http://flask.pocoo.org/snippets/32/

def index():
    strIO = StringIO.StringIO()
    strIO.write('Hello from Dan Jacob and Stephane Wirtel !')
    strIO.seek(0)
    return send_file(strIO,
                     attachment_filename="testing.txt",
                     as_attachment=True)

In case you need to use the snippet to support downloading a file which is stored as BLOB originally and to convert it as a downloadable file stream on the fly, then you can use io.BytesIO. See the below:

Let’s say exampleModel is the Sqlalchemy model object and blobField is a blob field which stores blob binary data,

buffer = io.BytesIO(exampleModel.blobField)
buffer.seek(0)    // You don’t need this
return send_file(buffer, attachment_filename=filename)

Thanks.

Heejune.

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