jay-diff
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 diff 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 diff 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