Why loops are needed in Python - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to print numbers from 1 to 3 using a loop.

Python

for i in [1]:
    print(i)

Drag options to blanks, or click blank then click option'

A[1, 2]

Brange(1, 4)

C3

Dlist

Attempts:

3 left

💡 Hint

Common Mistakes

Using a single number instead of a range.

Using a list with fewer numbers than needed.

The range(1, 4) function creates numbers 1, 2, 3 for the loop to print.

2fill in blank

medium

Complete the code to calculate the sum of numbers from 1 to 5.

Python

total = 0
for num in range(1, 6):
    total [1] num
print(total)

Drag options to blanks, or click blank then click option'

A+=

B*=

C-=

D/=

Attempts:

3 left

💡 Hint

Common Mistakes

Using subtraction or multiplication instead of addition.

Forgetting to update the total inside the loop.

The += operator adds each number to the total, accumulating the sum.

3fill in blank

hard

Fix the error in the code to print each character in the word.

Python

word = 'hello'
for [1] in word:
    print(letter)

Drag options to blanks, or click blank then click option'

Aletter

Bword

Cchar

Dletters

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different variable name in the loop and print.

Using the whole word instead of a single character.

The loop variable should be letter to match the print statement.

4fill in blank

hard

Fill both blanks to create a dictionary of squares for numbers 1 to 4.

Python

squares = {x: x[1]2 for x in range(1, 5) if x [2] 3}
print(squares)

Drag options to blanks, or click blank then click option'

A**

B>

C<

D+

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of power.

Using wrong comparison operators.

** is used for power, and < filters numbers less than 3.

5fill in blank

hard

Fill all three blanks to create a dictionary of uppercase keys and values greater than 1.

Python

result = [1]: [2] for k, v in data.items() if v [3] 1}
print(result)

Drag options to blanks, or click blank then click option'

Ak.upper()

Bv

C>

Dk

Attempts:

3 left

💡 Hint

Common Mistakes

Not converting keys to uppercase.

Using wrong comparison operator or variable names.

Keys are converted to uppercase with k.upper(), values are v, and filtered with > 1.

Practice

1. Why do we use loops in programming like Python?

easy

A. To store data permanently

B. To repeat actions multiple times without writing code again

C. To create new variables automatically

D. To stop the program from running

Solution

1. Step 1: Understand the purpose of loops

   Loops help us do the same task many times without writing the same code repeatedly.

2. Step 2: Compare options with loop purpose

   Only To repeat actions multiple times without writing code again matches this idea; others describe unrelated tasks.

3. Final Answer:

   To repeat actions multiple times without writing code again -> Option B

4. Quick Check:

   Loops repeat actions = To repeat actions multiple times without writing code again [OK]

Hint: Loops repeat tasks to save writing code again [OK]

Common Mistakes:

• Thinking loops store data permanently
• Confusing loops with variable creation
• Believing loops stop program execution

2. Which of the following is the correct syntax to start a for loop in Python?

easy

A. foreach i in range(5):

B. for i = 1 to 5:

C. loop i from 0 to 5:

D. for i in range(5):

Solution

1. Step 1: Recall Python for loop syntax

   Python uses 'for variable in iterable:' format, like 'for i in range(5):'.

2. Step 2: Check each option

   Only for i in range(5): matches Python syntax; others use incorrect or non-Python keywords.

3. Final Answer:

   for i in range(5): -> Option D

4. Quick Check:

   Python for loop = for i in range(5): [OK]

Hint: Python loops use 'for variable in iterable:' [OK]

Common Mistakes:

• Using 'for i = 1 to 5:' which is not Python syntax
• Using 'foreach' which is not a Python keyword
• Writing 'loop' instead of 'for'

3. What will be the output of this code?

for i in range(3):
    print(i)

medium

A. 0 1 2

B. 1 2 3

C. 0 1 2 3

D. 3 2 1

Solution

1. Step 1: Understand range(3) values

   range(3) generates numbers 0, 1, 2.

2. Step 2: Print each value in loop

   The loop prints each number on its own line: 0, then 1, then 2.

3. Final Answer:

   0 1 2 -> Option A

4. Quick Check:

   range(3) = 0,1,2 [OK]

Hint: range(n) starts at 0 up to n-1 [OK]

Common Mistakes:

• Thinking range(3) starts at 1
• Including 3 in output
• Reversing order of numbers

4. Find the error in this code:

i = 0
while i < 3
    print(i)
    i += 1

medium

A. i += 1 should be before print

B. Variable i should start at 1

C. Missing colon ':' after while condition

D. Indentation is wrong for print statement

Solution

1. Step 1: Check while loop syntax

   Python requires a colon ':' after the while condition.

2. Step 2: Identify missing colon

   The code misses ':' after 'while i < 3', causing syntax error.

3. Final Answer:

   Missing colon ':' after while condition -> Option C

4. Quick Check:

   while needs ':' = Missing colon ':' after while condition [OK]

Hint: Always put ':' after while and for conditions [OK]

Common Mistakes:

• Ignoring missing colon causing syntax error
• Changing variable start value unnecessarily
• Misplacing increment before print

5. You want to print all even numbers from 2 to 10 using a loop. Which code correctly uses a loop to do this?

hard

A. All of the above

B. for i in range(2, 11):
if i % 2 == 0:
print(i)

C. i = 2
while i <= 10:
print(i)
i += 2

D. for i in range(2, 11, 2):
print(i)

Solution

1. Step 1: Analyze for i in range(2, 11, 2): print(i)

   Uses for loop with step 2 from 2 to 10 inclusive, prints even numbers correctly.

2. Step 2: Analyze for i in range(2, 11): if i % 2 == 0: print(i) and C

   for i in range(2, 11): if i % 2 == 0: print(i) uses for loop with condition to print evens; i = 2 while i <= 10: print(i) i += 2 uses while loop incrementing by 2. Both print even numbers correctly.

3. Step 3: Understand All of the above

   Since A, B, and C all correctly print even numbers from 2 to 10, All of the above is correct.

4. Final Answer:

   All of the above -> Option A

5. Quick Check:

   All options print evens correctly = All of the above [OK]

Hint: Multiple loop styles can print even numbers correctly [OK]

Common Mistakes:

• Forgetting step in range for even numbers
• Not including 10 in range end
• Incorrect increment in while loop