When the np.concatenate function axis = 1, the output type question.

concatenate according to the numpy document:

Join a sequence of arrays along an existing axis.

(Interpretation) Join each array along axis.

Therefore

Therefore, np.concatenate ([grid, grid], axis=1) joins the sequence based on axis = 1. Illustrated as follows:

array ([[[1, 2, 3, 4, 5, 6], [1, 2, 3, 4, 5, 6]]) If you want to make a array ([1, 2, 3, 4, 5, 6]), I think you should use stacks, not join.

flatten_grid = grid.flatten()
np.array([flatten_grid, flatten_grid])
np.stack((flatten_grid, flatten_grid))