Django Object Update

dj-obj-update is a module that helps you do two things while updating an object:

1. Only do a save if something changed
2. Log what changed (the logger name is obj_update and only outputs logging.DEBUG)

Installation

pip install dj-obj-update

Usage

Updating an object

from obj_update import obj_update

new_data = {
    'flavor': 'chocolate',
}
for obj in queryset:
    obj_update(obj, new_data)

Dry run updating an object

from obj_update import obj_update

logger.setLevel(logging.DEBUG)  # see "Logging changes" below

new_data = {
    'flavor': 'chocolate',
}
for obj in queryset:
    obj_update(obj, new_data, update_fields=[])

Replacement for update_or_create

from obj_update import obj_update_or_create

choice, created = obj_update_or_create(
    Choice,
    question=question,
    defaults={'choice_text': 'Flour or corn?'},
)

Dealing with auto_now fields

By default, dj-obj-update constructs an update_fields when it saves. This means fields like the primary key, auto_now, and auto_now_add might not get saved. If you need these, you should set update_fields=None. Usage is the same as Django's update_fields

Logging changes

Using python-json-logger:

import logging
from pythonjsonlogger.jsonlogger import JsonFormatter

logger = logging.getLogger('obj_update')
handler = logging.FileHandler('log/my_obj_changes.log')
handler.setFormatter(JsonFormatter())
logger.addHandler(handler)
logger.setLevel(logging.DEBUG)

With JSON logging, you'll get messages like:

{"message": "[text hello->hello2]", "model": "FooModel", "pk": 1, "changes": {"text": {"old": "hello", "new": "hello2"}}}

With a normal logger, you'll still get output, but it won't have as much information:

[text hello->hello2]

You can selectively log object creation or updates. For example, if you don't expect objects to be created, you can only enable the obj_update.create logger. Likewise, you can only enable the obj_update.update logger to ignore creation. See the logging.config example at the top of test_obj_update for an example.