objdiff 1.2.3

Returns a list of commands/delta to go from one tree of objects to another

Take 2 sets of containers and provide a (deep) delta between them

This module is used by the author to diff yaml files and on disk file trees and best work out how to transition from one state to another (mainly for work with containers).

Note: Requires Python 3.3 or greater due to use of ‘yield from’

How?

Objdiff uses difflib built into python for lists and tuples (basically sorted things) and implements its own comparison code for dictionaries. User types are detected via the collections.abc.Mapping type and instance comparison and are treated as dictionaries (ie unsorted item => value mappings)

What does this look like?

>>> import objdiff
>>> a = {'a': 1, 'b':[1,2,3], 'c':None}
>>> b = {'a': 1, 'b':[1,4], 'c':'hello'}
>>> objdiff.obj_diff(a, b)
<generator object obj_diff at 0xb6a3da80>

We return an iterator and make use of yield from so you can process large trees of objects efficiently and incremental

>>> from pprint import pprint
>>> pprint(list(objdiff.obj_diff(a, b)))
[modified(path=['c'], old=None, new='hello'),
 modified(path=['b'], old=[1, 2, 3], new=[1, 4]),
 equal(path=['a'], old=1, new=1)]

Expanding out the generator we get back a bunch of tuples containing the command value, key path, before and after value

>>> c = {'a':{1: None, 2: 2, 3: 3}, 'b': None}
>>> d = {'a':{1: 1, 2: 2}, 'b': {'1':{}, '2':{'2':2}}}
>>> pprint(list(objdiff.obj_diff(c, d)))
[modified(path=['b'], old=None, new={'1': {}, '2': {'2': 2}}),
 modified(path=['a', 1], old=None, new=1),
 equal(path=['a', 2], old=2, new=2),
 deleted(path=['a', 3], val=3)]

Note: in the above how you get a full list of keys to the destined object after the command value.

In total there are 4 types of command, as listed below with one internal type that can be ignored.

• added

• deleted

• modified

• equal (internal, scalar values are equal)

More documentation can be found at Blitz works docs

Changelog

1.2.3 2016-08-26

• Actually include module with release

1.2.2 2016-03-28

• Split out CHANGELOG to seperate file

• Add documentation

• Add doctests

• Protection against PYTHONHASHSEED randomisation for doctests

• objdiff arg names where renamed to make relationship clearer

1.2.1 2016-03-26

• Add ‘version guard’ to prevent install on python older than version 3.3

1.2 2016-03-26

• Documentation updates

• ‘deep_update’ function

1.1 2016-03-24

• Cleanups of code

• Documentation updates

• More infrastructure in src module

1.0 2016-03-24

• Initial release

• Working objdiff

• diffing of lists and dicts functions