Construct 3 Dimensions Array From Two Dimensions Array Using Tile

I have an array arr = np.array([0.0, 0.0, 1.0]) I want to contract array of following shape promo_class.shape which is (2,3,3) I want to create repeated array of shape (2,3,3) arra

Solution 1:

Simply use np.broadcast_to for a view -

In [142]: arr = np.array([0.0, 0.0, 1.0])

In [144]: np.broadcast_to(arr,(2,3,3))
Out[144]: 
array([[[0., 0., 1.],
        [0., 0., 1.],
        [0., 0., 1.]],

       [[0., 0., 1.],
        [0., 0., 1.],
        [0., 0., 1.]]])

Why should we use view?

Because being a view, it has no extra memory overhead and hence virtually free on runtime -

In [148]: arr = np.random.rand(300)

In [149]: %timeit np.broadcast_to(arr,(200,300,300))
100000 loops, best of 3: 3.13 µs per loop

If you need an output with its own memory space, append with .copy().

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If you are devoted to np.tile -

In [174]: np.tile(arr,(2,3,1))
Out[174]: 
array([[[0., 0., 1.],
        [0., 0., 1.],
        [0., 0., 1.]],

       [[0., 0., 1.],
        [0., 0., 1.],
        [0., 0., 1.]]])