Module 1 · Lesson 2

Creating Arrays

There are three common families of array-creation functions:

Family	Functions	Use case
From existing data	`np.array`, `np.asarray`	You already have a list/tuple of values
Filled with a constant	`np.zeros`, `np.ones`, `np.full`, `np.eye`	You need a placeholder of a given shape
Evenly spaced ranges	`np.arange`, `np.linspace`	You need a sequence of numbers

np.arange(start, stop, step) works like Python’s range but returns an array and accepts floats. np.linspace(start, stop, num) instead fixes the count of points (inclusive of both ends by default), which is usually what you want for plotting.

print(np.zeros((2, 3)))
print()
print(np.full((2, 2), fill_value=7))
print()
print(np.eye(3))
print()
print(np.arange(0, 10, 2))       # stop is exclusive
print(np.linspace(0, 1, 5))      # stop is inclusive

Output:

[[0. 0. 0.]
 [0. 0. 0.]]

[[7 7]
 [7 7]]

[[1. 0. 0.]
 [0. 1. 0.]
 [0. 0. 1.]]

[0 2 4 6 8]
[0.   0.25 0.5  0.75 1.  ]

A quick preview before the next exercise — Module 2 covers indexing and slicing in full depth, but you’ll need a taste of it now. Slicing an array works just like slicing a Python list — arr[start:stop:step] — except it extends naturally to multiple axes by separating them with a comma. So arr[::2, ::2] means “every other row, every other column”: ::2 alone means “the whole axis, stepping by 2.”

grid = np.arange(16).reshape(4, 4)
print(grid)
print()
print(grid[::2, ::2])   # every other row, every other column

Output:

[[ 0  1  2  3]
 [ 4  5  6  7]
 [ 8  9 10 11]
 [12 13 14 15]]

[[ 0  2]
 [ 8 10]]

Write checkerboard(n) that returns an (n, n) array of int dtype containing a checkerboard pattern of 0s and 1s, where position (0, 0) is 1. For n=4 the result should be:

[[1 0 1 0]
 [0 1 0 1]
 [1 0 1 0]
 [0 1 0 1]]

💡 Hint

Build an (n, n) array of zeros with np.zeros, then use slicing with a step of 2 on rows and columns — board[0::2, 0::2] and board[1::2, 1::2] — to set the right cells to 1.

✅ Solution

def checkerboard(n):
    board = np.zeros((n, n), dtype=int)
    board[0::2, 0::2] = 1
    board[1::2, 1::2] = 1
    return board

Creating Arrays

Build a checkerboard