Steven’s answer is not correct. See the snapshot below. It is actually the reverse way.

Image transcribed as code:
>>> x = torch.tensor([[1,2],[3,4]],dtype=torch.float)
>>> F.softmax(x,dim=0)
tensor([[0.1192, 0.1192],
[0.8808, 0.8808]])
>>> F.softmax(x,dim=1)
tensor([[0.2689, 0.7311],
[0.2689, 0.7311]])