Best practice to reduce memory usage while splitting an array

Question

I have an array that I want to split in two halves. Due to symmetry, I'm only interested in keeping the left half of the array.

I can split the array in half by saying:

[a,b] = numpy.split(c,2)

where c is also an array.

Is there a way to return array 'a' or alternatively remove array "b" from memory immediately after splitting the array?

+3

Jonny 07 Sep 14 at 12:01

3 answers

You can use delete for this purpose . This is an example:

array=np.array([1,2,3,4])
x=len(array)/2
first_h=np.delete(array,array[x-1:])         #second half

Demo:

>>>print first_h
>>>[1,2]

+1

Kasramvd 07 Sep 14 at 12:04

I'm not sure, but I think it might be better because it relies on the implementation list

( docs ) and I'm sure everything was correct:

>>> r = range(10)
>>> r
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> del r[5:]
>>> r
[0, 1, 2, 3, 4]

0

ThinkChaos 07 Sep 14 at 12:43

6502 · Accepted Answer · 2014-09-07T12:15:07+0000

You can copy the first half with

a = x[len(x)//2:].copy()

this would allocate a copy and move the content (thus temporarily takes 1.5 times more memory)

Otherwise, you can just say

a = x[len(x)//2:]

to get a reference to the first half, but the other part will not be removed from memory