Unique entries

#!/usr/bin/env python

import json
import shelve
from urllib2 import urlopen

URL = 'http://54.200.3.128/examples/api.php'
DB_FILENAME = 'data.db'


def get_unique(url, db_filename):
    result = []
    db = shelve.open(DB_FILENAME)

    data = json.load(urlopen(URL))
    for entry in data:
        if str(entry['link_id']) not in db:
            result.append(entry)
            db[str(entry['link_id'])] = True

    db.close()
    return result


print(get_unique(URL, DB_FILENAME))