1. Lecture 23 – Practice Exercises 5
CMPT 120
Lecture 23 – Practice Exercises 5

2. Goals for Today! Practise hand tracing and commenting a program
Practise implementing an image processing program

3. Question 1 a) – Add comments:
Solution:
Question 1 a) – Add comments:
import random
def random_pie(pies):
pie1 = random.choice(pies)
pie2 = random.choice(pies)
if pie1 == pie2:
return (True, pie1, pie2)
return (False, pie1, pie2)
# Main part of program
pies = ("blueberry", "apple", "pecan")
pie_answer = random_pie(pies)
if pie_answer[0]:
print("You win a free " + pie_answer[1] + " pie!")
else:
print("You get a 5% discount on either " pie_answer[1] + " or " + pie_answer[2] + " pie!")

4. Question 1 b) Is pies A and pies B the same variable?
Solution:
Question 1 b)
Is pies A and pies B the same variable?
If not, what is pies A? What is pies B?
What is the scope of pies A? What is the scope of pies B?
import random
def random_pie(pies):
pie1 = random.choice(pies)
pie2 = random.choice(pies)
if pie1 == pie2:
return (True, pie1, pie2)
return (False, pie1, pie2)
# Main part of program
pies = ("blueberry", "apple", "pecan")
pie_answer = random_pie(pies)
if pie_answer[0]:
print("You win a free " + pie_answer[1] + " pie!")
else:
print("You get a 5% discount on either " pie_answer[1] + " or " + pie_answer[2] + " pie!") A B

5. Solution: https://repl.it/repls/PalatableFirsthandRam
Question 1 c)
Can you rewrite the function random_pie() such that it only has 1 return statement instead of 2?
import random
def random_pie(pies):
pie1 = random.choice(pies)
pie2 = random.choice(pies)
if pie1 == pie2:
return (True, pie1, pie2)
return (False, pie1, pie2)
# Main part of program
pies = ("blueberry", "apple", "pecan")
pie_answer = random_pie(pies)
if pie_answer[0]:
print("You win a free " + pie_answer[1] + " pie!")
else:
print("You get a 5% discount on either " pie_answer[1] + " or " + pie_answer[2] + " pie!")

6. raspberries.jpg Attribution: "Fir0002/Flagstaffotos"
Question 2
Given the image raspberries.jpg below, what does the code below output (approximately)? from PIL import Image rasp = Image.open("raspberries.jpg").load() # raspberries.jpg is 320 x 213 pixels print(rasp[160, 0][0]) print(rasp[0,212]) A
Looking at the image, the pixel at row 0, column 160 looks red so the value printed would be close to 255 – see arrow A
Looking at the image, the pixel at row 212, column 0 looks white so the colur value (r,g,b)
Printed would be close to (255, 255, 255) - B B
If you want to download this image, click on
“Other resolutions: 320 × 213 pixels ”
raspberries.jpg Attribution: "Fir0002/Flagstaffotos"

7. Question 3
What colour would a pixel with RGB value (0, 0, 50) appear to be?
(A) Dark red
(B) Light red
(C) Dark green
(D) Light green
(E) Dark blue
(F) Light blue

8. Question 4 Problem Statement:
Possible solution:
Question 4
Problem Statement:
Write a function that returns the colour of a given pixel as a string (using the table below)
Sample input: (0, 255, 0)
Function returns: “green”
Possible return values: “red”, “green”, “blue”, “white”, “black”, “yellow” or “magenta”