[Tutor] Test to check if values of dictionary are all equal (which happen to be dictionaries)

Peter Otten __peter__ at web.de
Sun Nov 9 19:56:12 CET 2014

Jignesh Sutar wrote:

> I needed to test if the values of all entries in a dictionary were equal
> but since the values themselves were dictionaries I couldn't simply take a
> set of the values and test if this equated to one. So I ended up taking
> all combination of the keys and testing pairs of sub dictionaries. I just
> want to check that there isn't a more direct way of doing this that
> testing all combinations?
> import itertools
> dictmain={"K1": {1:"SD_V1",2:"SD_V2"},
>           "K2": {1:"SD_V1",2:"SD_V2"},
>           "K3": {1:"SD_V1",2:"SD_V2"}}
> for compare in list(itertools.combinations(dictmain,2)):
>     print "Comparing dictionaries:", compare
>     if dictmain[compare[0]]==dictmain[compare[1]]:
>         print "comb dict are equal"
>     else:
>         print "comb dict are NOT equal"
>         break
> Many thanks in advance,
> Jignesh

If you don't have exotic data in your dicts equality should be transitive, 
i. e. from

a == b and a == c


b == c

so that you don't have to test the latter explicitly. 
This reduces the number of tests significantly.

values = dictmain.itervalues() # Python 3: iter(dictmain.values())
first = next(values) # pick an arbitrary value to compare against all others
if all(first == item for item in values):
    print("all dicts are equal")
    print("not all dicts are equal")

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