Get unique elements from a 2D list

问题

I have a 2D list which I create like so:

Z1 = [[0 for x in range(3)] for y in range(4)]

I then proceed to populate this list, such that Z1 looks like this:

[[1, 2, 3], [4, 5, 6], [2, 3, 1], [2, 5, 1]]

I need to extract the unique 1x3 elements of Z1, without regard to order:

Z2 = makeUnique(Z1) # The solution

The contents of Z2 should look like this:

[[4, 5, 6], [2, 5, 1]]

As you can see, I consider [1, 2, 3] and [2, 3, 1] to be duplicates because I don't care about the order.

Also note that single numeric values may appear more than once across elements (e.g. [2, 3, 1] and [2, 5, 1]); it's only when all three values appear together more than once (in the same or different order) that I consider them to be duplicates.

I have searched dozens of similar problems, but none of them seems to address my exact issue. I'm a complete Python beginner so I just need a push in the right direction.

I have already tried :

Z2= dict((x[0], x) for x in Z1).values() Z2= set(i for j in Z2 for i in j)

But this does not produce the desired behaviour.

Thank you very much for your help!

Louis Vallance

回答1:

If the order of the elements inside the sublists does not matter, you could use the following:

from collections import Counter

z1 = [[1, 2, 3], [4, 5, 6], [2, 3, 1], [2, 5, 1]]

temp = Counter([tuple(sorted(x)) for x in z1])

z2 = [list(k) for k, v in temp.items() if v == 1]
print(z2)  # [[4, 5, 6], [1, 2, 5]]

Some remarks:

• sorting makes lists [1, 2, 3] and [2, 3, 1] from the example equal so they get grouped by the Counter
• casting to tuple converts the lists to something that is hashable and can therefore be used as a dictionary key.
• the Counter creates a dict with the tuples created above as keys and a value equal to the number of times they appear in the original list
• the final list-comprehension takes all those keys from the Counter dictionary that have a count of 1.

---

If the order does matter you can use the following instead:

z1 = [[1, 2, 3], [4, 5, 6], [2, 3, 1], [2, 5, 1]]

def test(sublist, list_):
    for sub in list_:
        if all(x in sub for x in sublist):
            return False
    return True

z2 = [x for i, x in enumerate(z1) if test(x, z1[:i] + z1[i+1:])]
print(z2)  # [[4, 5, 6], [2, 5, 1]]

来源：https://stackoverflow.com/questions/45592455/get-unique-elements-from-a-2d-list