Hi! I can do that without any error
In [13]: a = torch.zeros(10, 10)

In [14]: b = torch.ones(3, 10)

In [15]: a[i] = b

In [16]: a
Out[16]:

    0     0     0     0     0     0     0     0     0     0
    1     1     1     1     1     1     1     1     1     1
    1     1     1     1     1     1     1     1     1     1
    1     1     1     1     1     1     1     1     1     1
    0     0     0     0     0     0     0     0     0     0
    0     0     0     0     0     0     0     0     0     0
    0     0     0     0     0     0     0     0     0     0
    0     0     0     0     0     0     0     0     0     0
    0     0     0     0     0     0     0     0     0     0
    0     0     0     0     0     0     0     0     0     0
[torch.FloatTensor of size 10x10]

Give us more information e.g. PyTorch’s version and your OS etc.