Get json data via url and use in python (simplejson)

Question

I imagine this must have a simple answer, but I am struggling: I want to take a url (which outputs json) and get the data in a usable dictionary in python. I am stuck on the last step.

>>> import urllib2
>>> import simplejson
>>> req = urllib2.Request("http://vimeo.com/api/v2/video/38356.json", None, {'user-agent':'syncstream/vimeo'})
>>> opener = urllib2.build_opener()
>>> f = opener.open(req)
>>> f.read()             # this works
'[{"id":"38356","title":"Forgetfulness - Billy Collins Animated Poetry","description":"US Poet Laureate Billy Collins reads his poem ","url":"http:\\/\\/vimeo.com\\/38356","upload_date":"2006-01-24 15:21:03","thumbnail_small":"http:\\/\\/80.media.vimeo.com\\/d1\\/5\\/47\\/74\\/thumbnail-4774968.jpg","thumbnail_medium":"http:\\/\\/80.media.vimeo.com\\/d1\\/5\\/46\\/85\\/thumbnail-4685118.jpg","thumbnail_large":"http:\\/\\/images.vimeo.com\\/87\\/39\\/873998\\/873998_640x480.jpg","user_name":"smjwt","user_url":"http:\\/\\/vimeo.com\\/smjwt","user_portrait_small":"http:\\/\\/bitcast.vimeo.com\\/vimeo\\/portraits\\/defaults\\/d.30.jpg","user_portrait_medium":"http:\\/\\/bitcast.vimeo.com\\/vimeo\\/portraits\\/defaults\\/d.75.jpg","user_portrait_large":"http:\\/\\/bitcast.vimeo.com\\/vimeo\\/portraits\\/defaults\\/d.100.jpg","user_portrait_huge":"http:\\/\\/bitcast.vimeo.com\\/vimeo\\/portraits\\/defaults\\/d.300.jpg","stats_number_of_likes":"281","stats_number_of_plays":"9173","stats_number_of_comments":23,"duration":"112","width":"320","height":"240","tags":"poetry, poet, online poetry, famous poet, video poetry, modern poetry, famous poem, poetry sites, poetry websites, audio poetry, american poet, animation clips, american poetry, free poetry sites, animation art, free poetry, animated clips, poem, poet laureate"}]'
>>> simplejson.load(f)
Traceback (most recent call last):
  File "<console>", line 1, in <module>
  File "/usr/lib/python2.5/site-packages/django/utils/simplejson/__init__.py", line 298, in load
    parse_constant=parse_constant, **kw)
  File "/usr/lib/python2.5/site-packages/django/utils/simplejson/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.5/site-packages/django/utils/simplejson/decoder.py", line 326, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.5/site-packages/django/utils/simplejson/decoder.py", line 344, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

Any ideas where I am going wrong?

Solution 1

Try

f = opener.open(req)
simplejson.load(f)

without running f.read() first. When you run f.read(), the filehandle's contents are slurped so there is nothing left when your call simplejson.load(f)

Solution 2

The first line reads the entire file. The second line then tries to read more from the file, but there's nothing left:

>>> f.read()             # this works
blah blah blah
>>> simplejson.load(f)

Either just omit the f.read() line, or save the value from read, and use it in loads:

json = f.read()
simplejson.loads(json)

Comments

[thornomad]

Thank you - I was just taking it step by step to make sure I could see the data ... obviously, don't know enough about read()! Thanks.

[Mead]

In python 3, simplejson is replaced with json, and it needs a conversion from bytes. data = json.loads(str(opener.open(req).read(),"utf-8")) will work for a UTF-8 encoded response.

[JeffS]

This requires that you absolutely trust the source of the json though

[Amanda]

@JeffS Can you explain why that is?

[JeffS]

Please see: docs.python.org/library/functions.html#eval So the the value of the json string is interpreted as python code, this means that you are allowing the code to be run as your program, and could be a major security issue.

[Kaolin Fire]

nit above—"utf-8" conversion goes with loads, not str (at least in python 2.7.3) ~ data = json.loads(str(opener.open(req).read()),"utf-8")

[Nathan Garabedian]

Instead of eval, look at the json library. json.loads() and json.dumps() converts between a python object and json string without the security issues of eval(). Otherwise this is a decent answer and thanks for the urllib2 code, that's what I was looking for.