How to create a 3D array in Python with Numpy?

Question

I want to create a 2x2x3 three-dimensional array in Python.

I did the following:

x = numpy.array([[[1,1], [2,2], [3,3]], [[1,1], [1,1], [1,1]]])

However, my output is a 2x3x2 array.

print(x.shape)

What did I wrong? And can anyone please explain step by step how to build a 3D array, I am a bit confused about the rows, colums and axis.

Thank you in advance.

If you do numpy.zeros((2,2,3)) you will see what an array of the desired shape (filled with zeros, obviously) looks like. — alani
– alani, Commented Jul 4, 2020 at 22:06

Furqan Hashim · Accepted Answer · 2020-07-04 22:35:59Z

3

This might be what you want

x = np.array([[[1,1,2], [2,3,3]], [[1,1,1], [1,1,1]]])
print(x.shape)
print(x)

Refer to this documentation for explanation.

What you created was an array with 3 rows, 2 columns and say 2 frames so you didn't get what you wanted (2 rows & 3 columns). We can make a 3d array representation as (frames, rows, columns).

Further you could've created an array with dimensions (n,) using

x = np.array([1, 1, 2, 2, 3, 3, 1, 1, 1, 1, 1, 1])

Then you can reshape it as per the requirement

For 2x2x3 you could do

x = x.reshape(2,2,3)

Similarly for 2x3x2

x = x.reshape(2,3,2)

edited Jul 4, 2020 at 22:35

answered Jul 4, 2020 at 22:06

Furqan Hashim

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3 Comments

Tom Over a year ago

This works :), Can you maybe explain your solution further? Or do you have tips/sources that explains this?

yatu Over a year ago

numpy.org/devdocs/user/absolute_beginners.html @tom

Furqan Hashim Over a year ago

@Tom I've made edit with an explanation. Hope it helps!

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