json_to_csv.py

import json
import unicodecsv as csv
import sys


def recursive_keys(row):
    keys = set()
    for k in row.keys():
        if isinstance(row[k], dict):
            for subkey in recursive_keys(row[k]):
                keys.add("%s.%s" % (k, subkey))
        else:
            keys.add(k)

    return keys


def recursive_get(d, key):
    key_list = key.split('.')
    val = d
    try:
        for key_item in key_list:
            val = val[key_item]
    except KeyError:
        return None

    return val


myjson = json.loads(open(sys.argv[1]).read())

try:
    relative_key = sys.argv[2]
    myjson = recursive_get(myjson, relative_key)
except:
    print "No relative keys"

keys = set()

for row in myjson:
    keys.update(recursive_keys(row))

mycsv = csv.DictWriter(sys.stdout, fieldnames=keys, quoting=csv.QUOTE_MINIMAL)
mycsv.writeheader()

for row in myjson:
    converted_row = {k: recursive_get(row, k) for k in keys}
    mycsv.writerow(converted_row)