Documentation on how to create an object only containing changed elements.

[samLozier]

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I'm trying to compare two json payloads. Essentially I want : diff_json = todays_json - yesterdays_json. It seems like this should be possible, but so far I haven't figured out how to do it. If it is, documentation would be helpful.

The end result should include the full original paths to the changed value, with all full-common keys and values removed.

eg:

# payload1 = {'a': [{'aa':'1'}, {'bb': '2'}]}
# payload2 = {'a': [{'aa':'2'}, {'bb': '2'}]}

# desired_output {'a': [{'aa': '2']}

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[samLozier]

This seems to work, but I'm not sure it's the best solution.

def diff_json(json1, json2):
  differences = DeepDiff(json1, json2, ignore_order=True).to_dict()

  def extract_changes(diffs):
    result = {}
    for change_type in ['values_changed', 'type_changes', 'dictionary_item_added', 'dictionary_item_removed',
                        'iterable_item_added', 'iterable_item_removed']:
      if change_type in diffs:
        for key, change in diffs[change_type].items():
          path = key.lstrip("root")
          if change_type == 'values_changed' or change_type == 'type_changes':
            # For value changes or type changes, we show the new value
            path = path.replace('[', '.[')  # Adjust path for lists
            set_nested_value(result, path, change['new_value'])
          elif change_type in ['dictionary_item_added', 'iterable_item_added']:
            path = path.replace('[', '.[')  # Adjust path for lists
            set_nested_value(result, path, change['value'])
          # For removed items, we skip them as we are only interested in the new state
    return result

  def set_nested_value(dct, path, value):
    keys = re.findall(r'\w+|\[\d+\]', path)
    current = dct
    for key in keys[:-1]:
      if re.match(r'\[\d+\]', key):  # If the key is a list index
        index = int(key[1:-1])
        while len(current) <= index:
          current.append({})
        current = current[index]
      else:
        if key not in current:
          current[key] = {}
        current = current[key]
    final_key = keys[-1]
    if re.match(r'\[\d+\]', final_key):
      index = int(final_key[1:-1])
      while len(current) <= index:
        current.append({})
      current[index] = value
    else:
      current[final_key] = value

  return extract_changes(differences)

output = diff_json(payload2, payload1)