Check if each element of a tensor is contained in a list

Question

Say I have a tensor A and a container of values vals. Is there a clean way of returning a Boolean tensor of the same shape as A with each element being whether that element of A is contained within vals? e.g:

A = torch.tensor([[1,2,3],
                  [4,5,6]])
vals = [1,5]

# Desired output
torch.tensor([[True,False,False],
              [False,True,False]])

Answer 1

You can achieve this with a for loop:

sum(A==i for i in B).bool()

Answer 2

You can simply do like this:

result = A.apply_(lambda x: x in vals).bool()

Then result will contain this tensor:

tensor([[ True, False, False],
        [False,  True, False]])

Here I simply used a lambda function and the apply_ method that you can find in the official documentation.

Answer 3

[list(map(lambda x: x in vals, thelist)) for thelist in A]

Answer 4

Use torch.isin method is the most convinient way. It's simple as follows: torch.isin(A, vals)