While loop execution flow in Python - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run the loop while count is less than 5.

Python

count = 0
while count [1] 5:
    print(count)
    count += 1

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

A<

B>

C==

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '>' instead of '<' causes the loop to never run.

Using '==' runs the loop only if count equals 5, which is not the goal.

The loop should continue while count is less than 5, so the condition is count < 5.

2fill in blank

medium

Complete the code to stop the loop when num reaches 10.

Python

num = 0
while num [1] 10:
    print(num)
    num += 2

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

A>

B<=

C<

D>=

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<=' causes the loop to run when num is 10, which may not be intended.

Using '>' or '>=' causes the loop to never run.

The loop should run while num is less than 10, so the condition is num < 10.

3fill in blank

hard

Fix the error in the loop condition to avoid an infinite loop.

Python

i = 5
while i [1] 0:
    print(i)
    i -= 1

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

A<=

B<

C>=

D>

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' causes the loop to never run.

Using '>=' or '<=' may cause off-by-one errors.

The loop should run while i is greater than 0, so the condition is i > 0. Using '<' would cause the loop to never run.

4fill in blank

hard

Fill both blanks to create a loop that prints numbers from 1 to 5.

Python

num = 1
while num [1] 5:
    print(num)
    num [2] 1

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

A<=

B+=

C-=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes 5 from the output.

Using '-=' decreases num, causing an infinite loop.

The loop should run while num is less than or equal to 5, and num should increase by 1 each time.

5fill in blank

hard

Fill all three blanks to create a loop that prints even numbers from 2 to 10.

Python

start = [1]
end = [2]
while start [3] end:
    print(start)
    start += 2

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

A2

B10

C<=

D<

Attempts:

3 left

💡 Hint

Common Mistakes

Using '<' excludes the last number 10.

Starting at 0 or 1 prints unwanted numbers.

The loop starts at 2, ends at 10, and runs while start is less than or equal to end.

Practice

1.

What does a while loop do in Python?

easy

A. Stops the program immediately

B. Runs code only once

C. Repeats code as long as a condition is true

D. Runs code a fixed number of times

Solution

1. Step 1: Understand the purpose of a while loop

   A while loop runs repeatedly while its condition is true.

2. Step 2: Compare options with this behavior

   Only Repeats code as long as a condition is true describes repeating code while a condition is true.

3. Final Answer:

   Repeats code as long as a condition is true -> Option C

4. Quick Check:

   While loop = repeat while true [OK]

Hint: While loops run repeatedly while condition is true [OK]

Common Mistakes:

• Thinking while loops run a fixed number of times
• Confusing while with if statement
• Believing while loops run only once

2.

Which of the following is the correct syntax to start a while loop in Python?

?

easy

A. while x > 0:

B. while (x > 0)

C. while x > 0 {}

D. while x > 0 then

Solution

1. Step 1: Recall Python while loop syntax

   Python uses a colon after the condition and no parentheses or braces.

2. Step 2: Match options with correct syntax

   while x > 0: uses 'while x > 0:' which is correct syntax.

3. Final Answer:

   while x > 0: -> Option A

4. Quick Check:

   Colon ends while condition line [OK]

Hint: Use colon after condition, no braces or 'then' [OK]

Common Mistakes:

• Adding braces {} like other languages
• Using 'then' keyword
• Putting condition in parentheses unnecessarily

3.

What will be the output of this code?

count = 3
while count > 0:
    print(count)
    count -= 1
print("Done")

medium

A. Done

B. 3 2 1 Done

C. 3 2 1 0 Done

D. 3 2 1 2 Done

Solution

1. Step 1: Trace the while loop iterations

   count starts at 3, prints 3, then decreases to 2, prints 2, then 1, then stops when count is 0.

2. Step 2: Note the final print after loop

   After loop ends, "Done" is printed.

3. Final Answer:

   3 2 1 Done -> Option B

4. Quick Check:

   Prints 3,2,1 then Done [OK]

Hint: Count decreases before loop ends, stops at zero [OK]

Common Mistakes:

• Expecting 0 to print inside loop
• Forgetting to decrease count
• Thinking loop runs forever

4.

Find the error in this code snippet:

i = 1
while i < 5
    print(i)
    i += 1

medium

A. Missing colon after while condition

B. Variable i is not initialized

C. Indentation error in print statement

D. Infinite loop because i never changes

Solution

1. Step 1: Check while loop syntax

   The while line must end with a colon (:).

2. Step 2: Identify the missing colon

   The code misses ':' after 'while i < 5', causing syntax error.

3. Final Answer:

   Missing colon after while condition -> Option A

4. Quick Check:

   While line needs colon [OK]

Hint: Always put colon after while condition [OK]

Common Mistakes:

• Forgetting colon after while
• Misindenting inside loop
• Not updating loop variable

5.

Consider this code:

n = 5
result = 1
while n > 1:
    result *= n
    n -= 1
print(result)

What does this code calculate?

hard

A. Sum of numbers from 1 to 5

B. Infinite loop with no output

C. Product of numbers from 1 to 4

D. Factorial of 5 (5!)

Solution

1. Step 1: Understand the loop's multiplication

   result multiplies by n each time, starting at 5 down to 2.

2. Step 2: Recognize factorial pattern

   Multiplying 5*4*3*2*1 equals 5 factorial (5!).

3. Final Answer:

   Factorial of 5 (5!) -> Option D

4. Quick Check:

   Multiplying down to 1 = factorial [OK]

Hint: Multiplying down from n to 1 calculates factorial [OK]

Common Mistakes:

• Thinking it sums numbers instead of multiplies
• Stopping multiplication at 2 instead of 1
• Assuming infinite loop