Python : simple array manipulation with Numpy

Question

Sorry for this simple question, but I can't find how to figure it out :

I have a long 1D numpy array like:

[1,2,3,4,5,6,7,8,9,10,11,12, ... ,n1,n2,n3]

this array is used to store x y z position of points, like [x0,y0,z0,x1,y1,z1 etc.... ]

I would like to convert it to this form :

[ [1,2,3],[4,5,6],[7,8,9],[10,11,12],....,[n1,n2,n3] ]

It it possible with numpy without going through slow for loops ?

Thanks :)

Answer 1

Use the reshape method.

a = np.arange(27) # some 1-D numpy array
a.reshape(-1, 3)

• Sven Marnach: Note that this doesn't loop over the data at all, i.e. not even in the C library code. It only creates a new view of the same data with different array strides pointing to the same region in memory as the original array.