jaydiff

Lightweight JSON diff / patch library for Python.

Computes the difference between two dicts and applies it back, with fine-grained control over which kinds of changes (add, update, delete) to track.

Installation

pip install .

API

Diff functions

Function	Description
jay_diff_add(old, new)	Keys present in new but absent in old
jay_diff_del(old, new)	Keys present in old but absent in new
jay_diff_upd(old, new)	Keys present in both whose values changed
jay_diff_upd_add(old, new)	Combined update + add
jay_diff_full(old, new, combine_upd_add=True)	Full diff; returns a dict with update_add/delete keys (or update/add/delete when combine_upd_add=False)

Merge functions

Function	Description
jay_merge_add(old, delta)	Apply an add-delta to old
jay_merge_delete(old, delta)	Apply a delete-delta to old
jay_merge_update(old, delta)	Apply an update-delta to old
jay_merge_full(old, diff)	Apply a full diff (output of jay_diff_full) to old

All operations are recursive — nested dicts are handled at every depth.

Usage

from jaydiff import jay_diff_full, jay_merge_full
from copy import deepcopy

old = {'soc': 80, 'range': 300, 'status': {'charging': True}}
new = {'soc': 75, 'range': 300, 'status': {'charging': False}, 'temp': 22}

diff = jay_diff_full(old, new)
# {'update_add': {'soc': 75, 'status': {'charging': False}, 'temp': 22}}

result = jay_merge_full(deepcopy(old), diff)
assert result == new

Delete semantics

When a key whose value is a dict is absent from new, the delete delta records None to signal "remove the entire key":

from jaydiff import jay_diff_del

jay_diff_del({'a': 1, 'b': {'x': 1, 'y': 2}}, {'a': 1})
# {'b': None}

jay_merge_full / jay_merge_delete interpret None as "delete this key entirely".

Running tests

pip install pytest
pytest