Loops — Python Practice Worksheet

Grades 9–12 Medium difficulty 10 problems

Loops repeat code while a condition is true (while) or iterate over a sequence (for). They eliminate repetitive code and are essential for processing collections and running simulations.

Python for loop: for i in range(5) runs i = 0,1,2,3,4. range(start, stop) excludes stop. while loops need a condition that eventually becomes false to avoid infinite loops.

Common patterns: accumulator (total += x), counter (count += 1), and finding max/min. Always check loop bounds and off-by-one errors.

Skills practiced

Writing for and while loops
Using range() correctly
Tracing loop output
Avoiding infinite loops

Name: Date: Period:

Practice Worksheet: Loops

Instructions: Solve each problem carefully. Show all work clearly. Write your final answer in the space provided or on a separate sheet as directed.

1.Write a for loop that prints the numbers from 1 to 10, each on a new line.

2.What is the output of the following code?

total = 0
for i in range(5):
    total += i
print(total)

3.Write a while loop that repeatedly asks the user to enter a number. The loop should stop when the user enters the number 0. For each number entered (except 0), print its square.

4.How many times will the following loop execute?

count = 0
while count < 10:
    print("Hello")
    count += 2

5.Use a for loop to calculate and print the sum of all even numbers between 1 and 20 (inclusive).
6.
What is the output of this code?
```
for i in range(3, 0, -1):
    print(i)
```
7.Write a loop that prints the multiplication table for the number 7 (from 1 to 10). Each line should show the multiplication and result, e.g., “7 x 1 = 7”.
8.Which of the following loops will run infinitely? (Circle all that apply)
1. A. (a)
2. B. (b)
3. C. (c)
4. D. (d)
9.Write a for loop that iterates over a list names = ["Alice", "Bob", "Charlie"] and prints each name in uppercase.
10.
The following code is supposed to print the numbers 1 through 5, but it has a bug. Identify the bug and write the corrected code.
```
num = 1
while num <= 5:
    print(num)
```

Answer Key

1.
Final answer:
```
for i in range(1, 11):
    print(i)
```
2.

The loop sums 0 + 1 + 2 + 3 + 4 = 10.

Final answer: 10

Final answer:

num = int(input("Enter a number: "))
while num != 0:
    print(num ** 2)
    num = int(input("Enter a number: "))

4.

The loop executes 5 times (count = 0, 2, 4, 6, 8).

Final answer: 5

Final answer:

total = 0
for num in range(2, 21, 2):
    total += num
print(total)

The sum is 110.

6.
Final answer:
```
3
2
1
```

Final answer:

for i in range(1, 11):
    print(f"7 x {i} = {7 * i}")

8.

Final answer: Options (a) and (d) will run infinitely.

Final answer:

names = ["Alice", "Bob", "Charlie"]
for name in names:
    print(name.upper())

10.
Final answer: The bug is that num is never incremented, so the loop runs infinitely. Corrected code:
```
num = 1
while num <= 5:
    print(num)
    num += 1
```

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Common mistakes to avoid

Off-by-one errors with range boundaries
Infinite while loops when condition never changes
Modifying loop variable incorrectly
Using for when while is clearer for unknown iterations

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Last updated: 2026

Loops — Python Practice Worksheet

Skills practiced

Answer Key

Common mistakes to avoid

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