How Pytorch Tensor get the index of specific value

I think there is no direct translation from list.index() to a pytorch function. However, you can achieve similar results using tensor==number and then the nonzero() function. For example:

t = torch.Tensor([1, 2, 3])
print ((t == 2).nonzero(as_tuple=True)[0])

This piece of code returns

1

[torch.LongTensor of size 1x1]

For multidimensional tensors you can do:

(tensor == target_value).nonzero(as_tuple=True)

The resulting tensor will be of shape number_of_matches x tensor_dimension. For example, say tensor is a 3 x 4 tensor (that means the dimension is 2), the result will be a 2D-tensor with the indexes for the matches in the rows.

tensor = torch.Tensor([[1, 2, 2, 7], [3, 1, 2, 4], [3, 1, 9, 4]])
(tensor == 2).nonzero(as_tuple=False)
>>> tensor([[0, 1],
        [0, 2],
        [1, 2]])

Can be done by converting to numpy as follows

import torch
x = torch.range(1,4)
print(x)
===> tensor([ 1.,  2.,  3.,  4.]) 
nx = x.numpy()
np.where(nx == 3)[0][0]
===> 2