How to dynamically create 3d numpy arrays from 2d numpy arrays using for loop

Question

I want to create a 3d numpy array form 2d numpy array using for loop.I tried in many different methods to create 3d arrays from 2d but each time its giving me errors. This is what I have done, the end array should have a dimension of (10,3,3).

#this is a sample code
arr=[]
for i in range(10):
    a=np.random.rand(3,3)
    arr=np.stack(a,arr)
    #arr=np.append(arr,a)
    #arr=np.array([arr,a])
    #arr[i]=a

akuiper · Accepted Answer · 2017-09-26 01:33:42Z

3

You can append the 2d arrays to the arr list using list.append method, and after you are done with the for loop, convert arr to 3d array by wrapping it with np.array:

arr = []
for i in range(10):
    a = np.random.rand(3,3)
    arr.append(a)

np.array(arr).shape
# (10, 3, 3)

Or numpy.stack:

np.stack(arr).shape
# (10, 3, 3)

answered Sep 26, 2017 at 1:33

akuiper

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