django file upload doesn't work: f.read() returns ''

Question

I'm trying to upload and parse json files using django. Everything works great up until the moment I need to parse the json. Then I get this error:

No JSON object could be decoded: line 1 column 0 (char 0)

Here's my code. (I'm following the instructions here, and overwriting the handle_uploaded_file method.)

def handle_uploaded_file(f, collection):
#  assert False, [f.name, f.size, f.read()[:50]]
  t = f.read()
  for j in serializers.deserialize("json", t):
    add_item_to_database(j)

The weird thing is that when I uncomment the "assert" line, I get this:

[u'myfile.json', 59478, '']

So it looks like my file is getting uploaded with the right size (I've verified this on the server), but the read command seems to be failing entirely.

Any ideas?

What's type(f) and t come out to? My suspicion is .read() works, but something isn't valid JSON. — Jason Goldstein
– Jason Goldstein, Commented Nov 15, 2011 at 20:00
From: assert False, [f.name, f.size, f.read()[:50], type(f), type(t), len(t)] I get, [u'wikileaks_comments.json', 59478, '', <class 'django.core.files.uploadedfile.InMemoryUploadedFile'>, <type 'str'>,0] — Abe
– Abe, Commented Nov 15, 2011 at 20:01
Re: not valid JSON -- That was my first guess too. But the file was created using simplejson, and I've run it through a validator. I'm pretty confident the json isn't the problem. — Abe
– Abe, Commented Nov 15, 2011 at 20:04

Jason Goldstein · Accepted Answer · 2011-11-15 20:06:31Z

2

I've seen this before. Your file has length, but reading it doesn't. I'm wondering if it's been read previously... try this:

f.seek(0)
f.read()

answered Nov 15, 2011 at 20:06

Jason Goldstein

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