json_to_csv.py

#!/usr/bin/env python

import collections
import json
import sys
import csv

Key = collections.namedtuple('Key', ['path', 'default'])
Field = collections.namedtuple('Field', ['label', 'key'])

# Mapping from CSV column name to key. Path is either a list of keys or a
# dot-delimited string (if there are no dots in your keys).
FIELDS = [
    Field('timestamp', Key('timestamp', None)),
    Field('user_id', Key('msg.user.id', None)),
    Field('mode', Key('msg.mode', None))
]


def get_deep(d, k, default):
    if not isinstance(k, list):
        k = k.split('.')
    f = k[0]
    k = k[1:]
    if k:
        if f in d:
            return get_deep(d[f], k, default)
        else:
            return default
    else:
        return d.get(f, default)


writer = csv.writer(sys.stdout)
writer.writerow([f.label for f in FIELDS])
for line in sys.stdin:
    body = json.loads(line)
    row = []
    for field in FIELDS:
        row.append(get_deep(body, field.key.path, field.key.default))
    writer.writerow(row)