json_set.py

#!/usr/bin/env python
"""
mbed tools
Copyright (c) 2018 ARM Limited
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
    http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
"""

#
# You can use command-line tools like 'jq' but they may not
# be common or available for your system. Python is common
# though, so here is one solution.

import argparse
import json
import sys


def prettyj(data):
    return json.dumps(data, separators=(',', ': '), sort_keys=True, indent=4)


def set(d, superkey, value):
    '''
    Given a dictionary, d, that contains dictionaries, drill down
    and set the new value.
      d = dictionary
      superkey = "k1.k2.k3.k4"
      value = the value you want to set
    '''
    current = d
    keys = superkey.split('.')
    try:
        for k in keys[0:-1]:
            current = current[k]
    except KeyError:
        print("ERROR: '%s' not found among keys: %s" % (k, sorted(current.keys())))
        sys.exit(1)
    current[keys[-1]] = value
    return d


if __name__ == '__main__':
    parser = argparse.ArgumentParser(epilog='''example use: python json_set.py mbed_app.json config.version.value '"2.0"' ''')
    parser.add_argument("filename", help="Filename of json file")
    parser.add_argument("key", help="The key to change. Use period '.' character for keys within keys.")
    parser.add_argument("value", help="The value to set for the given key.")
    args = parser.parse_args()

    with open(args.filename, 'r') as f:
        data = json.load(f)

    # Set the value
    result = set(data, args.key, args.value)

    with open(args.filename, 'w') as f:
         f.write(prettyj(data))
         print("Updated %s with '%s' = '%s'" % (args.filename, args.key, args.value))