Logic errors in Python
Name:
Date:
Class:
A
Quick Questions
Shade in the A or B circle for each question.
1. A program runs with no error message but prints the wrong total. What kind of mistake is it?
2. A game gives a pass mark for scores of 50 or more. Which condition is correct?
3. You want to print the numbers 1 to 5. Which loop does this?
4. Which code runs without an error message but is still a logic error?
5. A program should add 10% tax to a price. Which order of steps is correct?
B
Match the Pairs
Draw a line connecting each item on the left to its match on the right.
| Left column | Right column | |
|---|---|---|
| 1if score > 50: | Afor i in range(1, 11): | |
| 2for i in range(1, 5): | Baverage = total / 3 total = a + b + c | |
| 3A logic error: the average is worked out before the total has been added up, so the answer is wrong | CThe statements are in the wrong order, so print runs before total is set. Put total = 5 + 10 first, then print(total). | |
| 4Fixing an off-by-one error so a loop prints every number from 1 to 10 | DA 13 year old is left out because > was used instead of >=. Use age >= 13 to include 13. | |
| 5if age > 13: print("Teen") | ESkips a score of exactly 50, so a student who needs to score 50 or more to pass would wrongly fail | |
| 6print(total) total = 5 + 10 | FCounts only 1, 2, 3, 4 and stops before 5, so it is off by one if you wanted 1 to 5 |
C
Definitions
logic error
D
Fill in the Blanks
Complete each line of code by filling in the missing parts.
1.
score = 50
if score __ 50:
print("Pass")
2.
# Print the numbers 1 to 5
for i in range(1, _):
print(i)
3.
total = 0
total = total + 5
print(_____)
4.
score = 100
if score _ 100:
print("Bonus!")
5.
# Say hi 3 times
for i in range(_):
print("Hi")
E
Spot the Error
Shade in the letter of the line that contains an error.
Question 1
A
for i in range(1, 5):
B
print(i)
C
print('Done: 1 to 5')
Question 2
A
age = 13
B
print('13 and up only')
C
if age > 13:
D
print('Welcome')
Question 3
A
total = 0
B
print('Sum of 1 to 10')
C
for i in range(1, 10):
D
total = total + i
E
print(total)
Question 4
A
price = 20
B
discount = 5
C
pay = price + discount
D
print('You pay', pay)
Question 5
A
pass_mark = 50
B
score = 50
C
print('Pass mark is 50 or more')
D
if score > pass_mark:
E
print('Pass')
Answer Key
Logic errors in Python
Section A: Quick Questions
Q1
A — A logic error
Q2
A — if score >= 50:
Q3
A — for i in range(1, 6):
Q4
B — if age > 18: when 18-year-olds should be allowed in
Q5
B — price = 50, then total = price * 1.1, then print(total)
Section B: Match the Pairs
Q1
if score > 50: → Skips a score of exactly 50, so a student who needs to score 50 or more to pass would wrongly fail
Q2
for i in range(1, 5): → Counts only 1, 2, 3, 4 and stops before 5, so it is off by one if you wanted 1 to 5
Q3
A logic error: the average is worked out before the total has been added up, so the answer is wrong → average = total / 3
total = a + b + c
Q4
Fixing an off-by-one error so a loop prints every number from 1 to 10 → for i in range(1, 11):
Q5
if age > 13:
print("Teen") → A 13 year old is left out because > was used instead of >=. Use age >= 13 to include 13.
Q6
print(total)
total = 5 + 10 → The statements are in the wrong order, so print runs before total is set. Put total = 5 + 10 first, then print(total).
Section C: Definitions
Q1
logic error — A mistake that lets a program run with no error message but give the wrong result, caused by a wrong condition, operator (> or >=), range() off by one, or steps in the wrong order.Section D: Fill in the Blanks
Q1
score = 50
if score >= 50:
print("Pass")Q2
# Print the numbers 1 to 5
for i in range(1, 6):
print(i)Q3
total = 0
total = total + 5
print(total)Q4
score = 100
if score > 100:
print("Bonus!")Q5
# Say hi 3 times
for i in range(3):
print("Hi")Section E: Spot the Error
Q1
A — range(1, 5) stops before 5, so it only prints 1 to 4. The program still runs but gives the wrong result. To count 1 to 5 you need range(1, 6).
Q2
C — The rule says 13 and up, so a 13-year-old must be let in. With > a 13-year-old is rejected and no error shows. It should be if age >= 13:
Q3
C — range(1, 10) stops at 9, so 10 is never added and the total is wrong. It should be range(1, 11) to include 10.
Q4
C — A discount should lower the price, but + makes it higher. The program runs with no error but shows the wrong amount. It should be pay = price - discount.
Q5
D — The rule says 50 or more, so a score of exactly 50 should pass. With > a score of 50 fails and no error message shows. It should be if score >= pass_mark: