Python Loops (for, while) Exercises

Which of the following is the correct syntax of a `for` loop in Python?

for (i = 0; i < 5; i++):
    print(i)

for i in range(0,5):
    print(i)

for i to 5:
    print(i)

foreach i in range(5):
    print(i)

In Python, a for loop uses the in keyword and usually works with an iterable (like a list, tuple, string, or range).
The correct syntax is:

for variable in iterable:
    # loop body

Option 2 is correct: for i in range(0,5) iterates from 0 to 4.
Option 1 looks like C/Java syntax (not valid in Python).
Option 3 uses incorrect to keyword (Python doesn’t have it).
Option 4 uses foreach, which exists in other languages like PHP, but not in Python.

This tests whether learners can identify the basic correct syntax of a Python for loop.

Which statement best describes the difference between a `for` loop and a `while` loop in Python?

A for loop is used when the number of iterations is known, while a while loop is used when the condition must be checked until it becomes false.

A while loop is always faster than a for loop.

A for loop can only be used with numbers, while a while loop can be used with any type of data.

A for loop and while loop are exactly the same in Python.

for loop: Commonly used when the number of iterations is known in advance (e.g., iterating over a list, range, or string).
while loop: Used when we want to continue looping until a condition becomes false, and the number of iterations may not be known beforehand.
Option 1 correctly explains the key difference.
Option 2 is incorrect — speed depends on the task, not the loop type.
Option 3 is incorrect — for loops work with any iterable, not just numbers.
Option 4 is incorrect — they serve different purposes.

What will be the output of the following code?

for char in "Python":
    print(char, end=" ")

Python

P y t h o n

Pyt hon

P y t h o n

The for loop iterates over each character in the string "Python".
print(char, end=" ") prints each character followed by a space, instead of the default newline.
Output:

P y t h o n

Option 1: Default print without end=" " would print each character on a new line.
Option 2: Missing the trailing space after last character.
Option 3: Incorrect grouping of characters.

This demonstrates iteration over strings and customizing print behavior using the end parameter.

What will be the output of the following code?

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

1 2 3

0 1 2

0 1 2 3

3 2 1

range(3) generates numbers starting from 0 up to 3 (exclusive).
The for loop iterates over these values and prints them:

0
1
2

Option 1: Starts at 1 incorrectly.
Option 3: Includes 3, but range(3) stops before 3.
Option 4: Prints in reverse order, which is not the case here.

This shows the zero-based indexing behavior of Python’s range() and simple for loop iteration.

Which of the following situations is best suited for using a `while` loop instead of a `for` loop?

Iterating over a list of known length.

Repeating an action until the user types "exit".

Iterating over the numbers from 0 to 9.

Printing the first 10 even numbers.

while loops are ideal when the number of iterations is not known beforehand and depends on a condition.

Example:

command = ""
while command != "exit":
    command = input("Enter command: ")
    print("You entered:", command)

Option 1, 3, 4: Known number of iterations → better suited for a for loop.

This question emphasizes choosing the appropriate loop type based on the scenario.

What will be the output of the following code?

for i in range(5):
    if i == 3:
        break
    print(i)

0 1 2 3 4

3 4

0 1 2

0 1 2 3

The break statement exits the loop immediately when the condition i == 3 is True.
Iteration steps:
- i = 0 → printed
- i = 1 → printed
- i = 2 → printed
- i = 3 → break occurs, loop stops
Output:

0
1
2

Option 1: Ignores the break.
Option 2: Prints only after 3 → incorrect behavior.
Option 4: Includes 3, but loop exits before printing 3.

This demonstrates using break to stop a loop based on a condition.

What will be the output of the following code?

for i in range(5):
    if i % 2 == 0:
        continue
    print(i)

0 2 4

1 3 5

0 1 2 3 4

1 3

The continue statement skips the rest of the loop body for the current iteration if the condition is True.
Iteration steps:
- i = 0 → i % 2 == 0 → skip → not printed
- i = 1 → condition False → printed
- i = 2 → skip
- i = 3 → printed
- i = 4 → skip
Output:
```
1
3
```
Option 1: Prints even numbers → wrong
Option 2: Includes 5 → range(5) stops at 4
Option 3: Prints all numbers → ignores continue

This demonstrates using continue to selectively skip iterations in a loop.

Which of the following statements correctly describes a nested loop?

A loop inside a function.

A loop that executes only once.

A loop inside another loop.

A loop that runs in parallel with another loop.

A nested loop occurs when a loop is placed inside another loop.
Common use cases:
- Printing patterns (stars, numbers)
- Iterating over multi-dimensional data (like lists of lists or matrices)

Example:

for i in range(3):
    for j in range(2):
        print(i, j)

Output:

Option 1: Loop inside a function is not necessarily nested
Option 2: Loops can run multiple times
Option 4: Loops do not run in parallel by default in Python

Nested loops are important for complex iteration patterns and handling multi-level data structures.

What will be the output of the following code?

for i in range(2, 10, 3):
    print(i, end=" ")

2 5 8

2 3 4 5 6 7 8 9

0 3 6 9

2 5 7

range(start, stop, step) generates numbers starting from start up to stop (exclusive), incrementing by step.
Here: range(2, 10, 3) → numbers: 2, 5, 8
Output:
```
2 5 8
```
Option 2: Prints all numbers 2–9 sequentially → ignores step
Option 3: Starts from 0 → incorrect
Option 4: 7 is included incorrectly → should be 8

This demonstrates using step values in range() to control loop increments.

What will be the output of the following code?

total = 0
for i in range(1, 6):
    total += i
print(total)

15

10

5

20

The loop iterates over numbers from 1 to 5 (range(1,6) excludes 6).
total += i adds each number to total:
- 1 → total = 1
- 2 → total = 3
- 3 → total = 6
- 4 → total = 10
- 5 → total = 15
Output: 15
Option 2: Sum of 1–4 only → incorrect
Option 3: Only last iteration’s value → incorrect
Option 4: Sum over 1–6? → incorrect

This illustrates accumulating values using a loop.

What will be the output of the following code?

for i in range(1, 4):
    for j in range(1, 4):
        print(i * j, end=" ")
    print()

1 2 3 
2 4 6 
3 6 9

1 2 3 
2 3 4 
3 4 5

1 4 9 
1 4 9 
1 4 9

1 2 3 2 4 6 3 6 9

The outer loop (i) runs 1 to 3.
The inner loop (j) also runs 1 to 3.
i * j calculates multiplication for each pair (i,j).
end=" " prints on the same line, and print() without arguments moves to the next line after each inner loop.

Step by step:

i=1: 1*1=1, 1*2=2, 1*3=3 → 1 2 3
i=2: 2*1=2, 2*2=4, 2*3=6 → 2 4 6
i=3: 3*1=3, 3*2=6, 3*3=9 → 3 6 9
Option 2: Adds numbers instead of multiplying → incorrect
Option 3: Squares j only → incorrect
Option 4: Prints all numbers in one line → ignores line break

This demonstrates nested loops for pattern generation or tabular output.

What will be the output of the following code?

numbers = [3, 7, 2, 9, 4]
max_num = numbers[0]
for num in numbers:
    if num > max_num:
        max_num = num
print(max_num)

2

7

4

9

This code finds the maximum number in a list using a for loop.
Steps:
- max_num = 3 (initial)
- num = 3 → not greater → max_num = 3
- num = 7 → greater → max_num = 7
- num = 2 → not greater → max_num = 7
- num = 9 → greater → max_num = 9
- num = 4 → not greater → max_num = 9
Output: 9
Option 1,2,3: Do not consider the full comparison.

This illustrates finding the maximum value in a list using loops without built-in functions.

What will be the output of the following code?

n = 5
for i in range(1, n+1):
    print("*" * i)

*****
****
***
**
*

*
**
***
****
******

*
**
***
****
*****

    *
   **
  ***
 ****
*****

The loop runs i from 1 to 5 (range(1, n+1) includes 5).
"*" multiplied by i prints increasing stars each line, exactly 1 → 5 stars.
Output:

*
**
***
****
*****

Option 1: Prints decreasing stars → incorrect.
Option 2: Prints 6 stars on the last line → incorrect, because the loop stops at i = 5.
Option 4: Includes indentation → not in this code.

This demonstrates pattern printing using loops and string multiplication in Python.

What will the following code print?

count = 0
for i in range(2, 5):
    for j in range(1, i):
        count += j
print(count)

6

8

10

12

Outer loop: i takes values 2, 3, 4.
Inner loop: j runs from 1 up to i-1.

Step-by-step:

For i = 2: j = 1 → count = 0 + 1 = 1
For i = 3: j = 1, 2 → count = 1 + 1 + 2 = 4
For i = 4: j = 1, 2, 3 → count = 4 + 1 + 2 + 3 = 10

Final result printed = 10.

Option 1: Too low (misses contributions).
Option 2: Incorrect sum.
Option 4: Higher than actual.
Option 3: Correct.

This demonstrates nested loop accumulation logic.

Which code snippet will correctly print the numbers from 10 down to 1 (inclusive) using a `while` loop?

i = 10
while i < 1:
    print(i)
    i -= 1

i = 10
while i >= 1:
    print(i)
    i += 1

i = 1
while i <= 10:
    print(i)
    i -= 1

i = 10
while i >= 1:
    print(i)
    i -= 1

We want to start from 10 and print down to 1.
Correct loop:
- Initialize i = 10
- Condition: while i >= 1
- Decrement each step (i -= 1)

Why others are wrong:

Option 1: Wrong condition (i < 1), loop never runs.
Option 2: Increment instead of decrement → infinite loop.
Option 3: Starts at 1 and decrements → also infinite loop.

Therefore, only Option 4 works correctly.

What will this code print?

i = 0
while i < 5:
    i += 1
    if i == 3:
        continue
    print(i)

The loop starts with i = 0.
Each iteration: i is incremented first (i += 1).
When i == 3, the continue statement skips the print, so 3 is not printed.
Values printed: 1, 2, 4, 5.

Why others are wrong:

Option 1: Incorrect, includes 3 (but 3 is skipped).
Option 2: Starts with 0 (not possible, since i += 1 runs before print).
Option 4: Starts at 2, misses earlier prints.

Thus, the correct tricky output is 1, 2, 4, 5.

What will this code print?

for i in range(1, 6):
    if i % 2 == 0:
        continue
    for j in range(i):
        print(i, end=" ")
    print()

1 
3 3 3 
5 5 5 5 5

1 1 
3 3 
5 5

1 
3 
5

Outer loop: i goes from 1 to 5.
if i % 2 == 0: continue → skips even numbers (2 and 4).
Inner loop: prints i, repeated i times.
Actual output:
```
1 
3 3 3 
5 5 5 5 5
```

What will this code print?

for i in range(1, 4):
    for j in range(1, 4):
        if i == j:
            break
        print(i, j)

1 2
1 3
2 3

2 1
3 1
3 2

Outer loop: i = 1, 2, 3.
Inner loop: j = 1, 2, 3.
If i == j, the inner loop breaks (stops for that i).

Step-by-step:

i = 1: j = 1 → condition true → break immediately → nothing printed.
i = 2: j = 1 → not equal → print 2 1 → j = 2 → equal → break.
i = 3: j = 1 → not equal → print 3 1 → j = 2 → not equal → print 3 2 → j = 3 → equal → break.

Final output:

2 1
3 1
3 2

That matches Option 4.

Which code snippet will print `"Done"` only if the loop completes fully without hitting a `break`?

for i in range(5):
    if i == 2:
        break
else:
    print("Done")

for i in range(5):
    print(i)
else:
    print("Done")

for i in range(5):
    if i == 4:
        break
    print(i)
else:
    print("Done")

for i in range(5):
    print(i)
print("Done")

In Python, a for...else block runs the else part only if the loop is not terminated by break.
Option 2:
Loop runs from 0 → 4, printing all values.
No break → else executes, printing "Done".
Option 1: Has a break at i == 2, so "Done" never prints.
Option 3: Breaks at i == 4, so "Done" is skipped.
Option 4: Always prints "Done", but not using for...else.

Thus, the correct snippet is Option 2.

What will be the output of the following code?

i = 0
while i < 3:
    i += 1
    if i == 2:
        break
else:
    print("Completed")
print(i)

Completed
3

1
2
3

Completed
2

while i < 3: runs while i = 0 → 2.
i += 1 increments i each iteration.
When i == 2, break executes → loop exits immediately.
The else block does NOT execute because loop was terminated with break.
print(i) prints 2.

Step-by-step:

i = 0 → i = 1 → not 2 → continue
i = 1 → i = 2 → equals 2 → break → exit loop
else skipped → print(i) → 2

Python Loops (for, while) Exercises

Which of the following is the correct syntax of a for loop in Python?

Which statement best describes the difference between a for loop and a while loop in Python?

What will be the output of the following code?

What will be the output of the following code?

Which of the following situations is best suited for using a while loop instead of a for loop?

What will be the output of the following code?

What will be the output of the following code?

Which of the following statements correctly describes a nested loop?

What will be the output of the following code?

What will be the output of the following code?

What will be the output of the following code?

What will be the output of the following code?

What will be the output of the following code?

What will the following code print?

Which code snippet will correctly print the numbers from 10 down to 1 (inclusive) using a while loop?

What will this code print?

What will this code print?

Which code snippet will print "Done" only if the loop completes fully without hitting a break?

What will be the output of the following code?

About This Exercise: Python – Loops (for, while)

Which of the following is the correct syntax of a `for` loop in Python?

Which statement best describes the difference between a `for` loop and a `while` loop in Python?

Which of the following situations is best suited for using a `while` loop instead of a `for` loop?

Which code snippet will correctly print the numbers from 10 down to 1 (inclusive) using a `while` loop?

Which code snippet will print `"Done"` only if the loop completes fully without hitting a `break`?