python - JSON object could not be decoded

Question

I was trying to mine twitter data using tweepy and the data loaded into a JSON file , however the following code :

import tweepy
from tweepy import OAuthHandler
import json

consumer_key = '****'
consumer_secret = '****'
access_token = '****'
access_secret = '****'

auth = OAuthHandler(consumer_key, consumer_secret)
auth.set_access_token(access_token, access_secret)

api = tweepy.API(auth)

f = open('twitterdata.json', 'a+')

for status in tweepy.Cursor(api.home_timeline).items(10):
        json.dump(status._json, f)

line = f.readline()
tweet = json.loads(line)
print json.dumps(tweet, indent = 4)

produces the error :

Traceback (most recent call last):
  File "mytwittermine.py", line 21, in <module>
    tweet = json.loads(line)
  File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 364, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python2.7/json/decoder.py", line 382, in raw_decode
    raise ValueError("No JSON object could be decoded")
ValueError: No JSON object could be decoded

UPDATE

As suggested in one of the answers I now add a newline in every iteration of the for loop , so the code now is :

import tweepy
from tweepy import OAuthHandler
import json

consumer_key = '****'
consumer_secret = '****'
access_token = '****'
access_secret = '****'

auth = OAuthHandler(consumer_key, consumer_secret)
auth.set_access_token(access_token, access_secret)

api = tweepy.API(auth)

f = open('twitterdata.json', 'a+')

for status in tweepy.Cursor(api.home_timeline).items(10):
        json.dump(status._json, f)
        f.write('\n')

f.seek(0)
line = f.readline()
tweet = json.loads(line)
print json.dumps(tweet, indent = 4)

The above code gives the ValueError:

Traceback (most recent call last):
  File "mytwittermine.py", line 23, in <module>
    tweet = json.loads(line)
  File "/usr/lib/python2.7/json/__init__.py", line 339, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 367, in decode
    raise ValueError(errmsg("Extra data", s, end, len(s)))
ValueError: Extra data: line 1 column 3115 - line 2 column 1 (char 3114 - 301245)

Answer 1

You write to a file, then read withour rewinding, so nothing gets read. Add f.seek(0) between writing and reading.