convert numpy array of lists to array of int [duplicate]

Question

I have a 2D numpy array of single element lists:

aaa = np.array(
[[ [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0] ],
 [ [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0], [0] ],
 [ [0], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4], [4] ] ]
)

How can I turn the inner list into an int so I would have:

nnnn = np.array(
    [[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
     [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ],
     [0, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4 ]]
)

It sounds simple but anything I have tried I still end up with a list.

I tried sum() as a technique for summing the values in a list, but only ended up summing the whole lot.

I think the simplest solution is in the second dupe stackoverflow.com/questions/37152031/… - aaa[:,:,0] — Tomerikoo
– Tomerikoo, Commented Jul 7, 2022 at 8:38

Kins · Accepted Answer · 2022-07-08 08:55:22Z

-1

You can do:

nnnn = np.array([l.flatten() for l in aaa])

You can also use reshape:

nnnn = aaa.reshape(-1, aaa.shape[1])

Or even simpler:

nnnn = aaa[:,:,0]

It is useful to note that the last solution returns a view, not a copy. Meaning that changes you apply to the new array will also be reflected in the old array

edited Jul 8, 2022 at 8:55

answered Jul 7, 2022 at 8:28

Kins

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5 Comments

Tomerikoo Over a year ago

Or just aaa.reshape(arr.shape[:-1])

Tomerikoo Over a year ago

Or even simpler aaa[:,:,0]

jc508 Over a year ago

Thanks for the ideas everybody. I dont understand how this is interpreted as a change in dimensions though. I start with a 2D array and want to end with a 2D array. Regardless aaa[:,0] does what I want and gives an array of numbers

Kins Over a year ago

You actually start with a 3D array: aaa.shape returns (3,20,1)

Kins Over a year ago

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