numpy arrays: basic questions

Question

sorry if this question is so basic

A=np.arange(64).reshape(2,32)

array([[ 0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14, 15, 16,
        17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31],
       [32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48,
        49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63]])

A.reshape(4,4,4)

array([[[ 0,  1,  2,  3],
        [ 4,  5,  6,  7],
        [ 8,  9, 10, 11],
        [12, 13, 14, 15]],
       [[16, 17, 18, 19],
        [20, 21, 22, 23],
        [24, 25, 26, 27],
        [28, 29, 30, 31]],

       [[32, 33, 34, 35],
        [36, 37, 38, 39],
        [40, 41, 42, 43],
        [44, 45, 46, 47]],

       [[48, 49, 50, 51],
        [52, 53, 54, 55],
        [56, 57, 58, 59],
        [60, 61, 62, 63]]])

Now, i would have liked something like A[2] or A[2,:] or A[2,:,:] to return me the matrix

[[32, 33, 34, 35],
 [36, 37, 38, 39],
 [40, 41, 42, 43],
 [44, 45, 46, 47]]

and A[2,2,2] to return me 42 for example

but i got this error

IndexError: too many indices for array

You need to assign the reshaped array to a new variable before you can do that... — Forzaa
– Forzaa, Commented Apr 28, 2016 at 7:21

Mathias711 · Accepted Answer · 2016-04-28 07:21:58Z

2

You have to do

A = A.reshape(4,4,4)

instead of

A.reshape(4,4,4)

Because reshape is not inplace, you need to do this. Then you can do

A[2,2,2]
Out[301]: 42

answered Apr 28, 2016 at 7:21

Mathias711

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1 Comment

Fagui Curtain Over a year ago

lol ok, i thought it was a dumb question, and indeed it was thanks

co2y · Accepted Answer · 2016-04-28 07:23:43Z

0

after A.reshape(4,4,4) , A does not change

answered Apr 28, 2016 at 7:23

co2y

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1 Comment

hpaulj Over a year ago

Why the scold? I've seen plenty of answers the require further explanation. The question itself is implied. 'What's wrong or how do I do jt right?'.

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