Using Python to extract dictionary keys within a list

Question

I received a list when inputting the following URL - http://api.twitter.com/1/trends/44418.json

The list contains multiple dictionaries, and I'm a bit confused with the list structure. I'm trying to obtain the values associated with the 'name' key.

For example:

"name":"#throwagrenade" "name":"Rebecca Black" "name":"#questionsihate"

I can write the code myself, I'm just trying to conceptually understand how to access dictionaries (and their key/value pairs) within a list.

Answer 1

The first thing I would do when working with a big lump of json, is try to get it into a more readable format. This online json formatting tool should do the job.

Here's some code that will get all the trend names:

import urllib2
import json

url = 'http://api.twitter.com/1/trends/44418.json'

# download the json string
json_string = urllib2.urlopen(url).read()

# de-serialize the string so that we can work with it
the_data = json.loads(json_string)

# get the list of trends
trends = the_data[0]['trends']

# print the name of each trend
for trend in trends:
    print trend['name']

Or you can do it all in one line:

names = [trend['name'] for trend in the_data[0]['trends']]

for name in names:
    print name

Both will result in:

#throwagrenade
Rebecca Black
Eric Abidal
#questionsihate
#juniordoctors
Smiley Culture
Lily Allen
Wes Brown
Pandev
Ray Wilkins

Relevant reading:

Python docs on json (although you should only really need json.loads())

Dive Into Python's sections on lists and dictionaries.

Answer 2

Well, for a start, that link gives you JSON, so you'll need to deserialize it with the json library:

data = json.loads(response_data)

Now you simply have a list of dictionaries. You can easily iterate through the list with a for loop. On each iteration, you have a normal dictionary, from which you can get the value corresponding to the name key with the usual dictionary syntax.

You can do the whole thing at once with a simple list comprehension:

names = [item['name'] for item in data]

Answer 3

import urllib2
import json

url = 'http://api.twitter.com/1/trends/44418.json'
data = urllib2.urlopen(url).read()
j = json.loads(data)

names = [d['name'] for d in j[0]['trends']]

results in

names = [u'#throwagrenade', u'Rebecca Black', u'#questionsihate',
    u'#thingsthatdontgotogether', u'Eric Abidal', u'Smiley Culture',
    u'Ray Wilkins', u'Wes Brown', u'Twenty Twelve', u'Marseille']