Question

I have an upload form that accepts a zip file and has a method that unzips it and get each file from it. Make a unique id from the md5 hash of it and stores them in a dictionary;

dict[uid] = imagebinary

and returns it so that the form can store them into ZODB. I can’t store the image just like that, as this error spits out;

    2013-01-31 08:59:59,061 ERROR [waitress][Dummy-5] Exception when serving /
Traceback (most recent call last):
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/waitress-0.8.2-py2.7.egg/waitress/channel.py", line 329, in service
    task.service()
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/waitress-0.8.2-py2.7.egg/waitress/task.py", line 173, in service
    self.execute()
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/waitress-0.8.2-py2.7.egg/waitress/task.py", line 380, in execute
    app_iter = self.channel.server.application(env, start_response)
  File "/home/maverick/.buildout/eggs/pyramid-1.4-py2.7.egg/pyramid/router.py", line 251, in __call__
    response = self.invoke_subrequest(request, use_tweens=True)
  File "/home/maverick/.buildout/eggs/pyramid-1.4-py2.7.egg/pyramid/router.py", line 227, in invoke_subrequest
    response = handle_request(request)
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.4-py2.7.egg/pyramid_debugtoolbar/toolbar.py", line 133, in toolbar_tween
    body = tb.render_full(request).encode('utf-8', 'replace')
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.4-py2.7.egg/pyramid_debugtoolbar/tbtools.py", line 240, in render_full
    summary = self.render_summary(include_title=False, request=request)
  File "/home/maverick/inigo/sources/devenv/lib/python2.7/site-packages/pyramid_debugtoolbar-1.0.4-py2.7.egg/pyramid_debugtoolbar/tbtools.py", line 229, in render_summary
    'description':  description_wrapper % escape(self.exception),
UnicodeDecodeError: 'ascii' codec can't decode byte 0xef in position 114: ordinal not in range(128)

So, how should I go about doing that? I’m pretty much stuck on this.

Answer 1

The error you see is unrelated to image storing in the ZODB.

To store larger pieces of data, you really want to use a ZODB Blob instead of putting the image data directly in an attribute. Blobs are stored separately on disk and do not flush the ZODB cache, and can be streamed back to the client on access again.

To create and store a Blob, use:

from ZODB.blob import Blob

uid = Blob(imagebinary.read())

Once created like that, you can later use uid as a file; you need to open it in read or write mode first. To return the contents of the blob from a view, for example, use:

from pyramid.response import Response

def serveimage(request):
    # retrieve uid from somewhere
    resp = Response(content_type='image/jpeg')
    resp.app_iter = uid.open('r')  # open for reading
    return resp

Blobs are bound to transactions and changes to them are automatically discarded if the transaction is rolled back.