How to access a NumPy array by column

To access a NumPy array by column, you use array indexing. Remember, a NumPy array uses a 0-based index system.

Here's a step-by-step guide:

import numpy as np

array = np.array([[1, 2, 3], [4, 5, 6], [7, 8, 9]]) print(array)

This will give:

[[1 2 3] [4 5 6] [7 8 9]]

To access the first column:

first_column = array[:, 0] print(first_column)

Output:

[1 4 7]

For the second column:

second_column = array[:, 1] print(second_column)

Output:

[2 5 8]

And so on...

In general, to access the nth column, you would use:

nth_column = array[:, n-1]

The : symbol means you're taking all rows for the specified column index.