dict diff
so i came up with a diff method to compare 2 dicts. i found it pretty
useful so i thought i'd share it with everyone. you can see the doctest
to check out suggested uses. since we can't modify built-ins, i
demonstrated adding a diff method to OrderedDict to show how one could
add it to your own mapping objects.
the core logic is compatible with python2 and 3 (i've only tested using
2.6.5 and 3.1.2). the doctest is suited for python3 though.
the interface is pretty straightforward. it would be awesome to have
this sucker as a method on the builtin dict, but that'd take a pep, no?
--
Jin Yi
__author__ = 'razamatan_retral_net_ignore_com'
from collections import Mapping
def diffdict(left, right):
''' returns the deep diff of two dicts. the return value the tuple
(left_diff, right_diff)
>>> diffdict(1, None)
(1, None)
>>> diffdict({1:2}, None)
({1: 2}, None)
>>> diffdict({1:2}, {3:4})
({1: 2, 3: }, {1: , 3: 4})
>>> from collections import OrderedDict
>>> x = OrderedDict({1:2, 3:{4:{5:[6,7], 8:9}}})
>>> diffdict(x, x)
(None, None)
>>> y = {1:2, 3:[4]}
>>> diffdict(x, y)
({3: {4: {8: 9, 5: [6, 7]}}}, {3: [4]})
>>> y = {1:2, 3:{4:{5:[6,7]}}}
>>> diffdict(x, y)
({3: {4: {8: 9}}}, {3: {4: {8: }}})
>>> y = {1:2, 3:{4:{5:{6:7}, 8:9}}}
>>> diffdict(x, y)
({3: {4: {5: [6, 7]}}}, {3: {4: {5: {6: 7)
>>> del y[3]
>>> diffdict(x, y)
({3: {4: {8: 9, 5: [6, 7]}}}, {3: })
>>> y = {1:2, 3:{4:{5:[6,10], 8:9}}}
>>> diffdict(x, y)
({3: {4: {5: [6, 7]}}}, {3: {4: {5: [6, 10]}}})
>>> y = {1:100, 3:{4:{5:[6,7], 8:9}}}
>>> diffdict(x, y)
({1: 2}, {1: 100})
>>> diffdict(y, x)
({1: 100}, {1: 2})
>>> x.__class__.diff = diffdict
>>> x.__class__.__xor__ = diffdict
>>> x.diff(x)
(None, None)
>>> x ^ y
({1: 2}, {1: 100})
'''
# base case
if not isinstance(left, Mapping) or not isinstance(right, Mapping):
return (left, right)
# key exclusivity
left_diff = dict(i for i in left.items() if i[0] not in right)
right_diff = dict(i for i in right.items() if i[0] not in left)
right_diff.update((k, KeyError) for k in left_diff if k not in right_diff)
left_diff.update((k, KeyError) for k in right_diff if k not in left_diff)
# value differences
for k in (k for k in left if k in right):
if left[k] != right[k]:
(ld, rd) = diffdict(left[k], right[k])
left_diff[k] = ld or None
right_diff[k] = rd or None
left_diff = left_diff or None
right_diff = right_diff or None
return (left_diff, right_diff)
--
http://mail.python.org/mailman/listinfo/python-list
Re: dict diff
i don't think this piece of code is obscure. i think the use case is there when you know that dicta != dictb, but you need to know where they're different. i wouldn't really care to have it on the dict since it's useful as an unbound method anyway. On Sat, Nov 20, 2010 at 01:11:53AM -0500, Steve Holden wrote: > On 11/19/2010 8:58 PM, Jin Yi wrote: > > so i came up with a diff method to compare 2 dicts. i found it pretty > > useful so i thought i'd share it with everyone. you can see the doctest > > to check out suggested uses. since we can't modify built-ins, i > > demonstrated adding a diff method to OrderedDict to show how one could > > add it to your own mapping objects. > > > > the core logic is compatible with python2 and 3 (i've only tested using > > 2.6.5 and 3.1.2). the doctest is suited for python3 though. > > > > > > the interface is pretty straightforward. it would be awesome to have > > this sucker as a method on the builtin dict, but that'd take a pep, no? > > > > > > > A PEP *and* some explanation of why you would want such an obscure piece > of code built in to the dict object, yes. > > regards > Steve > -- > Steve Holden +1 571 484 6266 +1 800 494 3119 > PyCon 2011 Atlanta March 9-17 http://us.pycon.org/ > See Python Video! http://python.mirocommunity.org/ > Holden Web LLC http://www.holdenweb.com/ > > -- > http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: dict diff
right. i moved to a 2-value tuple return value basically to illustrate exactly
where each dict is providing a different value. it turns out to be much easier
to grok than the 3-value one since it's all there and lines up correctly with
the inputs...
On Sat, Nov 20, 2010 at 12:00:16PM +, Steven D'Aprano wrote:
> On Sat, 20 Nov 2010 01:11:53 -0500, Steve Holden wrote:
>
> > On 11/19/2010 8:58 PM, Jin Yi wrote:
> >> so i came up with a diff method to compare 2 dicts.
> [...]
> > A PEP *and* some explanation of why you would want such an obscure piece
> > of code built in to the dict object, yes.
>
> You've never wanted to see how two dicts differ, as well as the fact that
> they do? I frequently find myself wanting to see why two dicts that
> should be equal aren't, especially for testing and debugging.
>
> I use this function:
>
> def dict_diffs(a, b):
> """dict_diffs(adict, bdict) -> (amissing, bmissing, different)
>
> Returns sets (amissing, bmissing, different) such that:
>
> amissing = keys missing from adict compared to bdict
> bmissing = keys missing from bdict compared to adict
> different = keys in both adict and bdict but with different values
>
> >>> dict_diffs({1:0, 2:0, 3:0}, {1:1, 2:0, 4:0})
> (set([4]), set([3]), set([1]))
>
> """
> from collections import Mapping
> if not isinstance(a, Mapping) and isinstance(b, Mapping):
> raise TypeError('arguments must both be mappings')
> amissing, bmissing, different = set(), set(), set()
> for key, value in a.items():
> if key not in b:
> bmissing.add(key)
> elif value != b[key]:
> different.add(key)
> for key, value in b.items():
> if key not in a:
> amissing.add(key)
> return (amissing, bmissing, different)
>
>
> --
> Steven
> --
> http://mail.python.org/mailman/listinfo/python-list
--
I pops mah collah. (Busta Rhymes)
Jin Yi -- http://www.retral.net/razamatan
--
http://mail.python.org/mailman/listinfo/python-list
