How to check for redundant combinations in a python dictionary -

i have following python dictionary tuples keys , values:

{(a, 1): (b, 2),  (c, 3): (d, 4),  (b, 2): (a, 1),  (d, 4): (c, 3),  } 

how unique set of combinations between keys , values? such (a,1):(b,2) appears, not (b,2):(a,1)?

d = {('a', 1): ('b', 2),      ('c', 3): ('d', 4),      ('b', 2): ('a', 1),      ('d', 4): ('c', 3),     }  >>> dict(set(frozenset(item) item in d.items())) {('a', 1): ('b', 2), ('d', 4): ('c', 3)} 

this works converting each key/value pair in dictionary set. important because pair (a, b), set([a, b]) equal set([b, a]). perfect if take of key/value sets , add them set, eliminate of duplicates. can't set type because isn't hashable, use frozenset instead. built-in dict() function can accept iterable of key/value pairs argument, can pass in our set of key/value pairs , work expected.

a great point made in comments causing issue if maps itself, example if had d[('a', 1)] = ('a', 1), work around can use sorted() suggested in comment:

d = {('a', 1): ('a', 1),      ('c', 3): ('d', 4),      ('d', 4): ('c', 3),     }  >>> dict(sorted(item) item in d.items()) {('a', 1): ('a', 1), ('c', 3): ('d', 4)} 

this has benefit duplicates sorted order consistently give "smaller" of elements key , "larger" value.

however on python 3.x need careful if keys , values may have different types, since sorted() raise exception unless of elements in iterable same type:

>>> d = {1: 'a', 'a': 1} >>> dict(sorted(item) item in d.items()) traceback (most recent call last):   file "<stdin>", line 1, in <module>   file "<stdin>", line 1, in <genexpr> typeerror: unorderable types: int() < str()