numpy array not changing value on assignment

Question

I have the following python program:

import numpy as np
x = np.array([[1,2],[3,5],[4,6]])
some_list = [1,2]
x[some_list][:,1]=100

The numpy array "x" still remains unchanged after the above execution.
The above code is a small working example of what I want to do!
So, I have a list (of indices) and a numpy array.
I want to change a column (for example column with index 1 in the above program) in all rows indexed by the list.
What is the smallest and the easiest to understand piece of code doing this?
The above code doesn't work as expected, why so?

Sunderam Dubey · Accepted Answer · 2022-05-30 17:43:01Z

1

You need to combine the different pairs of []:

x[some_list, 1] = 100

Output:

>>> x
array([[  1,   2],
       [  3, 100],
       [  4, 100]])

edited May 30, 2022 at 17:43

Sunderam Dubey

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answered May 26, 2022 at 16:46

user17242583

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