Python - basic command for extracting a JSON response item

Question

I'm only a few days into my Python experience so I'm sorry to pollute the site with a baby-steps question. I'm trying to write an add-on for XBMC, which I believe uses Python 2.4. I've accessed a web api, which wraps the return in JSON. I've saved the url return to a WebHTML list (I think a list!). When I enter the following from the stackoverflow tutorial:

decoded = json.loads(WebHTML)
print 'DECODED:', decoded

I get the following in my log:

NOTICE: {u'totalItems': 1, u'query': u'Ludwig van Beethoven Op 67 Symphony No 5 in Cm (Fate)', u'kind': u'volumes#volumes', u'items': [{u'scoreId': u'IMSLP01056', u'pageCount': 42, u'title': u'Symphony No.5, Op.67 - Complete Score (S.464/5)', u'kind': u'volumes#volume', u'authors': [u'Beethoven, Ludwig van'], u'year': 1807, u'selfLink': u'http://www.peachnote.com/rest/api/v0/score?id=IMSLP01056'}]}

I want to extract the scoreId for a subsequent url call, i.e. IMSLP01056, but I'm struggling with the correct command. When I try:

dict = json.loads(WebHTML)
dict['items']['scoreId']
print dict['items']['scoreId']

The log error returned is:

TypeError: list indices must be integers, not str

If I try:

print dict[4][1]

it returns

KeyError: (4,)

I've tried a variety of JSONloads commands but can't get any to work. I always get an error beginning:

IOError: (2, 'No such file or directory', '{\n "kind": "volumes#volumes",\n "query": "Ludwig ..... etc, etc.

So, I'm a little stumped as to the correct command I should use. Thanks and sorry if this is too much info for a very basic question.

Using dict as a variable name is a very bad idea as it shadows the built-in name. — Fred Foo
– Fred Foo, Commented Apr 30, 2013 at 9:52
Thanks larsmans, I've changed 'dict' to 'scoreId', though I still get the same error. — user2335216
– user2335216, Commented Apr 30, 2013 at 9:56

Daniel Roseman · Accepted Answer · 2013-04-30 09:56:46Z

2

The main response you're getting is indeed a dictionary, but the value for its items key is a list. So the error is telling you to use an integer index for that inner lookup. So:

dict['items'][0]['scoreId']

Note that there are potentially many items inside that items list, and the above will only give you the first: you probably want all of them in a single list:

scores = [item['scoreId'] for item in dict['items']]

which will iterate through all items, and extract their scores into a separate list.

Also, as larsmans says, don't use dict (or list) as a variable name, as it hides the built-in dict() function.

answered Apr 30, 2013 at 9:56

Daniel Roseman

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1 Comment

user2335216 Over a year ago

Ooh, now it does work. Sorry, I forgot to amend the preceding line as well. Thanks everyone - told you I was a beginner!! Can't believe how quickly you helped.

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