python-session-01-debug-quiz.md

Debug Quiz: Session 01 Foundations

Question 1

There are two errors. Fix the function so it correctly counts items in a list.

Broken:

def my_len(data)
    count = 0
    for item in data:
        count =+ 1
    return count

Fixed:

def my_len(data):
    count = 0
    for item in data:
        count += 1
    return count

Type: debug Hint: Start at line 1, then check the counter update on line 4. Explanation: Function definitions need :, and count += 1 increments the counter correctly.

Question 2

There are two errors. Fix the script to print all valid indexes.

Broken:

data = [10, 20, 30, 40]

for i in range(len(data) + 1):
    print(data[i

Fixed:

data = [10, 20, 30, 40]

for i in range(len(data)):
    print(data[i])

Type: debug Hint: Look at the loop bound first, then check the print line punctuation. Explanation: range(len(data) + 1) goes out of bounds; also print is missing a closing parenthesis.

Question 3

There is one logic error. Fix the script so it safely handles an empty list when computing the average.

Broken:

# The list can have any number of values, from empty ("No data") to hundreds.

data = [10,20,30]

total,count = 0,0

for x in data:
    total += x
    count += 1

print(total / count)

Fixed:

data = [10,20,30]

total,count = 0,0

for x in data:
    total += x
    count += 1

if count != 0:
    print(total / count)
else:
    print("No data")

Type: debug Hint: Check what happens if the list is empty before dividing by count. Explanation: Dividing by count is unsafe when count == 0; add a guard so empty input prints a safe message.