Hands-on: Array slicing

Source code for this exercise is located in numpy/array-slicing/

First, create a 4×4 array with arbitrary values, then

1. Extract every element from the second row.
2. Extract every element from the third column.
3. Assign a value of 0.21 to upper left 2×2 subarray.

Next, create a 8×8 array with chequerboard pattern, i.e. alternating zeros
and ones:

1 0 1 ...
0 1 0 ...
1 0 1 ...
 ...

How many statements you do need for creating the pattern?