CODEWITHSUNDEEP
pythonpython-3.xnumpynumpy-ndarray
BlackHawk
BlackHawk

Reputation: 861

Filling 3D numpy array with one variable dimension

I would like to fill a 3D numpy array which has dimension (?, 100, 100). The first dimension will range between 500 and 1000 but is not known beforehand. I could use the append method, but this is slow.

Is there another posibility to create such a 3D numpy array where the first dimension is not known beforehand? The numpy array is filled using a for loop.

Second, let's assume I have the following two numpy arrays:

import numpy as np
arr1 = np.random.randint(0, 100, size=(30, 100, 100))
arr2 = np.random.randint(0, 100, size=(50, 100, 100))

How can I concatenate arr1 and arr2 along the first dimension so that the resulting array has shape (80, 100, 100)?

Upvotes: 2

Views: 1521

Answers (1)

DeepBlue
DeepBlue

Reputation: 448

About the first question, I always use np.empty and np.append methodes which are totaly fine.

arr = np.empty((0, 100, 100), int)
arr = np.append(arr,x,axis=0)

about the second question, append works well again:

arr3  = np.append(arr1, arr2, axis=0)

also 'concatenate' is usable:

arr3  = np.concatenate((arr1, arr2), axis=0)

Upvotes: 2

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