JSON to python dictionary: Printing values

Question

Noob here. I have a large number of json files, each is a series of blog posts in a different language. The key-value pairs are meta data about the posts, e.g. "{'author':'John Smith', 'translator':'Jane Doe'}. What I want to do is convert it to a python dictionary, then extract the values so that I have a list of all the authors and translators across all the posts.

for lang in languages:
   f = 'posts-' + lang + '.json'
   file = codecs.open(f, 'rt', 'utf-8')
   line = string.strip(file.next())
   postAuthor[lang] = []
   postTranslator[lang]=[]

   while (line):
      data = json.loads(line)
      print data['author']
      print data['translator']

When I tried this method, I keep getting a key error for translator and I'm not sure why. I've never worked with the json module before so I tried a more complex method to see what happened:

  postAuthor[lang].append(data['author'])
  for translator in data.keys():
      if not data.has_key('translator'):
           postTranslator[lang] = ""
      postTranslator[lang] = data['translator']

It keeps returning an error that strings do not have an append function. This seems like a simple task and I'm not sure what I'm doing wrong.

Have you tried print data in the first version after json.loads? What does it output? — g.d.d.c
– g.d.d.c, Commented Jul 18, 2011 at 19:46
It prints the entire content of the blog post, all of the the meta data, etc. in key-value format. — MRose429
– MRose429, Commented Jul 18, 2011 at 20:10
Can you paste in a sample of the data structure? There's nothing wrong with the code in the first example that would cause the error you're receiving unless the data isn't complete. Maybe try printing data.keys() and make sure there's not a space in 'translator' or something to that effect. You could also try data.get('translator', ''), which will fill in a blank string if the translator isn't set for a post. — g.d.d.c
– g.d.d.c, Commented Jul 18, 2011 at 20:18
I don't think this will help you with your problems, but in your second section of code you have an if statement where you're checking if 'translator' is a key in data. Right after that, however, you try to access the key 'translator' even if it doesn't exist. You may want to think about putting an else statement after that if not data.has_key(...) — Bryce Siedschlaw
– Bryce Siedschlaw, Commented Jul 18, 2011 at 22:54

jessejlt · Accepted Answer · 2011-07-19 01:50:05Z

See if this works for you:

import json

# you have lots of "posts", so let's assume
# you've stored them in some list. We'll use
# the example text you gave as one of the entries
# in said list

posts = ["{'author':'John Smith', 'translator':'Jane Doe'}"]

# strictly speaking, the single-quotes in your example isn't
# valid json, so you'll want to switch the single-quotes
# out to double-quotes, you can verify this with something
# like http://jsonlint.com/
# luckily, you can easily swap out all the quotes programmatically

# so let's loop through the posts, and store the authors and translators
# in two lists
authors = []
translators = []

for post in posts:
    double_quotes_post = post.replace("'", '"')
    json_data = json.loads(double_quotes_post)

    author = json_data.get('author', None)
    translator = json_data.get('translator', None)

    if author: authors.append(author)
    if translator: translators.append(translator)

# and there you have it, a list of authors and translators

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