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pythonpython-2.7settuplesunique

Getting unique tuples out of a python set

I currently have a set like the following:

{(a,b), (b,a), (c,b), (b,c)}

What I Would like to have is:

{(a,b), (c,b)}

As you may notice the duplicate values have been removed completely so that two tuples never have the same elements inside regardless of order.

How can I tell the set to disregard the order of the elements in the tuple and just check the values between the tuples?

Solution

  • Okay, so you've got a set {c1, c2, c3, ...}, where each cN is itself a collection of some sort.

    If you don't care about the order of the elements in cN, but do care that it is unique (disregarding order), then cN should be a frozenset1 rather than a tuple:

    >>> orig = {("a", "b"), ("b", "a"), ("c", "b"), ("b", "c")}
>>> uniq = {frozenset(c) for c in orig}
>>> uniq
{frozenset(['b', 'a']), frozenset(['b', 'c'])}

    As a general rule, choosing an appropriate data type from those provided by Python is going to be more straightforward than defining and maintaining custom classes.

    1 It can't be a set, because as a member of a larger set it needs to be hashable.