Recursive diff for nested structures
Project description
Nested-Diff.py
Recursive diff for python nested structures, implementation of Nested-Diff
Builtin containers traversed recursively, all other types compared by values.
Diff format
Diff is a dict and may contain following keys:
A
stands for 'added', it's value - added item.D
means 'different' and contains subdiff.E
diffed entity (optional), value - empty instance of entity's class.I
index for sequence item, used only when prior item was omitted.N
is a new value for changed item.O
is a changed item's old value.R
key used for removed item.U
represent unchanged item.
Diff metadata alternates with actual data; simple types specified as is, dicts,
lists and tuples contain subdiffs for their items with native for such types
addressing: indexes for lists and tuples and keys for dictionaries. Each status
type, except D
. E
and I
, may be omitted during diff computation. E
tag
is used with D
when entity unable to contain diff by itself (set, frozenset);
D
contain a list of subdiffs in this case.
Annotated example:
a: {"one": [5,7]}
b: {"one": [5], "two": 2}
opts: U=False # omit unchanged items
diff:
{"D": {"one": {"D": [{"I": 1, "R": 7}]}, "two": {"A": 2}}}
| | | | | | || | | | | | | | |
| | | | | | || | | | | | | | +- with value 2
| | | | | | || | | | | | | +- key 'two' was added
| | | | | | || | | | | | +- subdiff for it
| | | | | | || | | | | +- another key from top-level
| | | | | | || | | | +- what it was (item's value: 7)
| | | | | | || | | +- what happened to item (removed)
| | | | | | || | +- list item's actual index
| | | | | | || +- prior item was omitted
| | | | | | |+- subdiff for list item
| | | | | | +- it's value - list
| | | | | +- it is deeply changed
| | | | +- subdiff for key 'one'
| | | +- it has key 'one'
| | +- top-level thing is a dict
| +- changes somewhere deeply inside
+- diff is always a dict
Examples
>>> from nested_diff import diff, patch
>>>
>>> a = {'one': 1, 'two': 2, 'three': 3}
>>> b = {'one': 1, 'two': 42}
>>>
>>> diff(a, b)
{'D': {'three': {'R': 3}, 'two': {'O': 2, 'N': 42}, 'one': {'U': 1}}}
>>>
>>> diff(a, b, O=False, U=False)
{'D': {'two': {'N': 42}, 'three': {'R': 3}}}
>>>
>>>
>>> c = [0,1,2,3]
>>> d = [ 1,2,4,5]
>>>
>>> diff(c, d, O=False, U=False)
{'D': [{'R': 0}, {'I': 3, 'N': 4}, {'A': 5}]}
>>>
>>>
>>> c = patch(c, diff(c, d))
>>> assert c == d
Subclassing
from nested_diff import Differ
class CustomDiffer(Differ):
"""
Use custom precision for floats.
"""
def __init__(self, float_precision=2, *args, **kwargs):
super().__init__(*args, **kwargs)
self.set_differ(float, self.diff_float)
self.float_precision = float_precision
def diff_float(self, a, b):
if round(a, self.float_precision) == round(b, self.float_precision):
return {'U': a} if self.op_u else {}
return super().diff__default(a, b)
differ = CustomDiffer(float_precision=1, U=False)
a = [0.001, 0.01, 0.1]
b = [0.002, 0.02, 0.2]
assert {'D': [{'I': 2, 'N': 0.2, 'O': 0.1}]} == differ.diff(a, b)
License
Licensed under the terms of the Apache License, Version 2.0.
See Also
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