intercept dictionary items which are two dimensional array

Question

Here is my dictionary of n items.

{
"proceed": [[6,46] , [7,67], [12,217], [67,562], [67,89]],
"concluded":  [[6,46] , [783,123], [121,521], [67,12351], [67,12351]],
...

}

imagine a dictionary s.t. like that with n keys and items which are two dimensional arrays.

I want to intercept all of them and take the result as [6,46]

I tried s.t. like that :

result=set.intersection(*map(set,output.values()))

however it got error because of items are two dimensinal array.

Can someone please help me how to do that ?

Thanks.

Do you mean [intersect](https://en.wikipedia.org/wiki/Intersection_(set_theory))? Not [intercept](https://en.wiktionary.org/wiki/intercept)? Also, what is your *expected output*? — FHTMitchell, Mar 08 '18 at 17:29
@FHTMitchell: OP gave us the expected output: that one pair, [6, 46] — Prune, Mar 08 '18 at 17:32

FHTMitchell · Answer 1 · 2018-03-08T17:39:06.630

3

So... sets don't work for lists because lists are not hashable. Instead you'll have to make them sets of tuples like so:

result = set.intersection(*({tuple(p) for p in v} for v in output.values()))

Edit: works in py version >= 2.7

edited Mar 08 '18 at 17:39

answered Mar 08 '18 at 17:35

FHTMitchell

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The first one works fine on later versions of Python 2 – Martin Evans Mar 08 '18 at 17:37
@MartinEvans Ah yes I forgot they backported set literals to 2.7 – FHTMitchell Mar 08 '18 at 17:38

score 0 · Answer 2 · answered Mar 08 '18 at 18:07

Completely agree with answer of @FHTMitchell but here's a bit of more explanation with example of why you can't get unique set with list and get TypeError: unhashable type

Consider below values:

x = {'concluded': [[6, 46], [783, 123], [121, 521], [67, 12351], [67, 12351]],
 'proceed': [[6, 46], [7, 1], [12, 217], [67, 562], [67, 89]]}
y = {'concluded': ((6, 46), (67, 12351), (121, 521), (783, 123)),
 'proceed': ((6, 46), (7, 1), (12, 217), (67, 89), (67, 562))}

x is the dictionary containing list of list as values; the main thing to note is that value of keys are stored as list which is mutable; but in y it's tuple of tuples or you may keep it as set which is not mutable

Now consider some how you managed to get your desire output [6,46] but if you notice it's a list contains some elements stored in a list so if you change the values as below:

x['proceed'][0][0] = 9

it will change your value [6, 46] to [9,46] in concluded key and now your output may or may not change which depends on how you iterated and stored it.

intercept dictionary items which are two dimensional array

2 Answers2