Numpy reshape array of arrays to 1D

Question

How do I get x to become a 1D array? I found it convenient to create x like this,

x=np.array([[0,-1,0]*12,[-1,0,0]*4])
print x
print len(x)

returns

array([ [0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0],
       [-1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0]], dtype=object)

2

I also tried making it like this, but the length is still 2

y=((0,1,0)*12,(-1,0,0)*4)
print y

returns

((0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 1, 0), (-1, 0, 0, -1, 0, 0, -1, 0, 0, -1, 0, 0))

I have tried using numpy.reshape (on both x and y):

np.reshape(x,48)

but I get this error:

ValueError: total size of new array must be unchanged

Is it possible to reshape x or y when I have declared them like I did?

Your x is 2 lists of different length, 36 and 12. Do you want one of length 48? — hpaulj
– hpaulj, Commented Jun 20, 2015 at 14:25

user2357112 · Accepted Answer · 2015-06-20 06:17:03Z

2

When you create the array, concatenate the lists with + instead of packing them in another list:

x = np.array([0,-1,0]*12 + [-1,0,0]*4)

answered Jun 20, 2015 at 6:17

user2357112

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Comments

nitin · Accepted Answer · 2015-06-20 06:09:38Z

0

I think you are looking to make a 1D numpy array that has a length of 48. Try,

    import numpy as np
    x=np.array([[0,-1,0]*12])
    x= np.append(x,[-1,0,0]*4)
    print (x)
    print (len(x))

This yields,

[ 0 -1  0  0 -1  0  0 -1  0  0 -1  0  0 -1  0  0 -1  0  0 -1  0  0 -1  0  0
 -1  0  0 -1  0  0 -1  0  0 -1  0 -1  0  0 -1  0  0 -1  0  0 -1  0  0]
48

answered Jun 20, 2015 at 6:09

nitin

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1 Comment

Matt Majic Over a year ago

Thanks. I actually have a longer array that has more of those groups of 12 so I wanted to create it in a single line like with the + method above.

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