python 2-D list how to make a set [duplicate]

Answer 1

The most typical solutions have already been posted, so let's give a new one:

Python 2.x

list1 = [[1, 2], [3, 4], [1, 2]]
list2 = {str(v): v for v in list1}.values()

Python 3.x

list1 = [[1, 2], [3, 4], [1, 2]]
list2 = list({str(v): v for v in list1}.values())

Answer 2

There is no inbuilt single function to achieve this. You have received many answers. In addition to those, you may also use a lambda function to achieve this:

list(map(list, set(map(lambda i: tuple(i), list1))))

Answer 3

You can try this:

list1 = [[1,2],[3,4],[1,2]]
list2 = []
for i in list1:
    if i not in list2:
        list2.append(i)
print(list2)
[[1, 2], [3, 4]]

Answer 4

That will do:

>>> list1 = [[1,2],[3,4],[1,2]]
>>> list2 = list(map(list, set(map(tuple,list1))))
>>> list2
[[1, 2], [3, 4]]

Answer 5

Note that this only removes duplicate sublists, it does not take into account the sublist's individual elements. Ex: [[1,2,3], [1,2], [1]] -> [[1,2,3], [1,2], [1]]

>>> print map(list, {tuple(sublist) for sublist in list1})
[[1, 2], [3, 4]]

Answer 6

Unfortunately, there is not a single built-in function that can handle this. Lists are "unhashable" (see this SO post). So you cannot have a set of list in Python.

But tuples are hashable:

l = [[1, 2], [3, 4], [1, 2]]
s = {tuple(x) for x in l}

print(s)

# out: {(1, 2), (3, 4)}

Of course, this won't help you if you want to later, say, append to these lists inside your main data structure, as they are now all tuples. If you absolutely must have the original list functionality, you can check out this code recipe for uniquification by Tim Peters.