Python JSON Tool for doog

json_replace.py

import json
import sys

def main():
    num_args = len(sys.argv)

    if num_args < 4:
        print 'Invalid arguments, should be <file> <key> <value>'
    else:
        file_name = sys.argv[1]
        key = sys.argv[2]
        val = sys.argv[3]

        # Load JSON File
        with open(file_name, "r") as json_file:
            json_data = json.load(json_file)
        
            # Replace key with value
            json_replace(json_data, key, val)

            # Write it back
            with open(file_name, "w") as write_file:
                json_str = json.dumps(json_data, sort_keys=True, indent=2)
                write_file.write(json_str)
                print 'Done.'

def json_replace(data, key, val):
    # Key may reference nested objects with period syntax
    key_split = key.split('.')

    # Get to deepest level
    to_change = data
    for nested_key in key_split[:-1]:
        to_change = to_change[nested_key]

    # Change the value
    last_key = key_split[-1]
    to_change[last_key] = val

# Run Main
main()