import torch
import torch.nn.utils.rnn as rnn_utils

a = torch.tensor([[1,2],[2,2],[3,3],[3,2],[3,2]])
b = torch.tensor([[4,2],[5,1],[4,4]])
c = torch.tensor([[6,9]])
result = rnn_utils.pad_sequence([a, b, c])

tensor([[[1, 2],
         [4, 2],
         [6, 9]],

        [[2, 2],
         [5, 1],
         [0, 0]],

        [[3, 3],
         [4, 4],
         [0, 0]],

        [[3, 2],
         [0, 0],
         [0, 0]],

        [[3, 2],
         [0, 0],
         [0, 0]]])