How to zero particular elements using a mask in python?

I ran into a simple problem, where I wanted to assign values according to a mask that represents a position of elements in an array. For instance array[*,1] = 0 but this code obviously would not work.

After a little thought I have come up with this:

import numpy as np

a = np.random.normal(size=(5, 2))

print(a)
print(a.shape)

for i in np.arange(a.shape[0]):
    a[i][1] = 0
    
print(a)
print(a.shape)

But obviously, this awkward loop is not a pythonic way of doing that.

So, can you share some neat ways of performing such operations in Python?

>Solution :

Just slice the array with a[:, 1] = 0 if you want all entries of the first column to be zero.

If you want to use a condition statement look into np.where, which can be used to index the array according to a[np.where(condition)] = 0