json object diff

diff_json.py

#!/usr/bin/env python

import sys
import json

def diff_objects(left, right):
    if not (type(left) == type(right) == dict):
        return right
    result = {}
    keys = set()
    keys.update(left.keys())
    keys.update(right.keys())
    for key in keys:
        left_child, right_child = left.get(key, None), right.get(key, None)
        if left_child != right_child:
            result[key] = diff_objects(left_child, right_child)
    return result

def apply_diff(obj, diff):
    for key, child_diff in diff.items():
        child = obj.get(key, None)
        if child_diff == None:
            del obj[key]
        elif not (type(child) == type(child_diff) == dict):
            obj[key] = child_diff
        else:
            apply_diff(child, child_diff)

if __name__ == "__main__":
    (left_path, right_path) = sys.argv[1:]
    def load(path):
        with open(path) as f:
            return json.load(f)
    left, right = load(left_path), load(right_path)
    diff = diff_objects(left, right)
    sys.stdout.write(json.dumps(diff, indent=2, sort_keys=True))
    sys.stdout.write("\n")

    apply_diff(left, diff)
    assert(left == right)