NumPy Exercises

Question 1

Import NumPy as np

Answer 1

import numpy as np

Question 2

Create an array of 10 zeros

Answer 2

np.zeros(10)

Question 3

Create an array of 10 ones

Answer 3

np.ones(10)

Question 4

Create an array of 10 fives

Answer 4

np.ones(10) * 5

Question 5

Create an array of the integers from 10 to 50

Answer 5

np.arange(10,51)

Question 6

Create an array of all the even integers from 10 to 50

Answer 6

np.arange(10,51,2)

Question 7

Create a 3x3 matrix with values ranging from 0 to 8

Answer 7

np.arange(9).reshape(3,3)

Question 8

Create a 3x3 identity matrix

Answer 8

np.eye(3)

Question 9

Use NumPy to generate a random number between 0 and 1

Answer 9

np.random.rand(1)

Question 10

Use NumPy to generate an array of 25 random numbers sampled from a standard normal distribution

Answer 10

np.random.randn(25)

Question 11

Create the following matrix:

array([[ 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, 0.07, 0.08, 0.09, 0.1 ],
[ 0.11, 0.12, 0.13, 0.14, 0.15, 0.16, 0.17, 0.18, 0.19, 0.2 ],
[ 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3 ],
[ 0.31, 0.32, 0.33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39, 0.4 ],
[ 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5 ],
[ 0.51, 0.52, 0.53, 0.54, 0.55, 0.56, 0.57, 0.58, 0.59, 0.6 ],
[ 0.61, 0.62, 0.63, 0.64, 0.65, 0.66, 0.67, 0.68, 0.69, 0.7 ],
[ 0.71, 0.72, 0.73, 0.74, 0.75, 0.76, 0.77, 0.78, 0.79, 0.8 ],
[ 0.81, 0.82, 0.83, 0.84, 0.85, 0.86, 0.87, 0.88, 0.89, 0.9 ],
[ 0.91, 0.92, 0.93, 0.94, 0.95, 0.96, 0.97, 0.98, 0.99, 1. ]])

Answer 11

np.arange(1,101).reshape(10,10) / 100

Question 12

Create an array of 20 linearly spaced points between 0 and 1:

Answer 12

np.linspace(0,1,20)

Question 13

array([[ 1, 2, 3, 4, 5],
[ 6, 7, 8, 9, 10],
[11, 12, 13, 14, 15],
[16, 17, 18, 19, 20],
[21, 22, 23, 24, 25]])

Answer 13

mat = np.arange(1,26).reshape(5,5)
mat

Question 14

where mat = np.arange(1,26).reshape(5,5)
mat :

array([[12, 13, 14, 15],
[17, 18, 19, 20],
[22, 23, 24, 25]])

Answer 14

mat[2:,1:]

Question 15

where mat = np.arange(1,26).reshape(5,5)
mat :

20

Answer 15

mat[3,4]

Question 16

where mat = np.arange(1,26).reshape(5,5)
mat :

array([[ 2],
[ 7],
[12]])

Answer 16

mat[:3,1:2]

Question 17

where mat = np.arange(1,26).reshape(5,5)
mat :

array([21, 22, 23, 24, 25])

Answer 17

mat[4,:]

Question 18

where mat = np.arange(1,26).reshape(5,5)
mat :

array([[16, 17, 18, 19, 20],
[21, 22, 23, 24, 25]])

Answer 18

mat[3:5,:]

Question 19

Get the sum of all the values in mat

Answer 19

mat.sum()

Question 20

Get the standard deviation of the values in mat

Answer 20

mat.std()

Question 21

Get the sum of all the columns in mat

Answer 21

mat.sum(axis=0)