Iterate over numpy array to fill a python list

Question

I'm iterating over a numpy array to apply a function through each element and add the new value to a list so I can keep the original data.

The problem is: it's kinda slow.

Is there a better way to do this (without changing the original array)?

import numpy as np
original_data = np.arange(0,16000, dtype = np.float32)
new_data = [i/max(original_data) for i in original_data]
print('done')

Saullo G. P. Castro · Accepted Answer · 2015-09-26 15:17:49Z

2

You could simply do:

new_data = original_data/original_data.max()

Numpy already performs this operation element-wise.

In your code there is an extra source of slowness: each call max(original_data) will result in an iteration over all elements from original_data, making your cost proportional to O(n^2).

edited Sep 26, 2015 at 15:17

answered Sep 26, 2015 at 15:12

Saullo G. P. Castro

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1 Comment

Victor José Over a year ago

Thank you very much. This approach will help alot.

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