Exercise

Python Control Structures

These exercises are designed to help you practice working with control structures in Python. Follow each step carefully and try to predict the output before running the code.

File Organization

We'll add a new directory called control_structures to your existing file structure. The updated structure will look like this:

csf101-python_exercises/
│
├── basics/
│   ├── numbers.py
│   ├── strings.py
│   └── booleans.py
│
├── data_structures/
│   ├── lists.py
│   └── dictionaries.py
│
├── operators/
│   ├── arithmetic.py
│   ├── assignment.py
│   ├── comparison.py
│   ├── logical.py
│   └── bitwise.py
│
└── control_structures/
    ├── conditionals.py
    ├── loops.py
    └── break_continue.py

Create a new directory called control_structures inside your csf101-python_exercises directory.

Exercise 1: Conditional Statements

File: control_structures/conditionals.py

Create a new file called conditionals.py in the control_structures directory and complete the following exercises in this file.

Write an if-else statement to check if a number is positive or negative.

number = 10
if number > 0:
    print("The number is positive.")
else:
    print("The number is non-positive.")

Expected output: The number is positive.

Extend the previous example to include zero as a separate case.

number = 0
if number > 0:
    print("The number is positive.")
elif number < 0:
    print("The number is negative.")
else:
    print("The number is zero.")

Expected output: The number is zero.

Write a program that assigns a letter grade based on a numerical score.

score = 85
if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "F"
print(f"Your grade is: {grade}")

Expected output: Your grade is: B

Use a ternary operator to check if a number is even or odd.
```
number = 7
result = "even" if number % 2 == 0 else "odd"
print(f"The number is {result}.")
```
Expected output: The number is odd.

Implement a simple calculator using if-elif-else statements.

num1 = 10
num2 = 5
operator = "+"

if operator == "+":
    result = num1 + num2
elif operator == "-":
    result = num1 - num2
elif operator == "*":
    result = num1 * num2
elif operator == "/":
    result = num1 / num2 if num2 != 0 else "Error: Division by zero"
else:
    result = "Error: Invalid operator"

print(f"Result: {result}")

Expected output: Result: 15

Exercise 2: Loops

File: control_structures/loops.py

Create a new file called loops.py in the control_structures directory and complete the following exercises in this file.

Write a for loop to print numbers from 1 to 5.
```
for i in range(1, 6):
    print(i)
```
Expected output:
```
1
2
3
4
5
```
Use a while loop to print numbers from 5 to 1 in reverse order.
```
count = 5
while count > 0:
    print(count)
    count -= 1
```
Expected output:
```
5
4
3
2
1
```
Write a for loop to calculate the sum of numbers from 1 to 10.
```
total = 0
for num in range(1, 11):
    total += num
print(f"The sum of numbers from 1 to 10 is: {total}")
```
Expected output: The sum of numbers from 1 to 10 is: 55

Use a for loop to iterate over a list and print each item.

fruits = ["apple", "banana", "cherry"]
for fruit in fruits:
    print(fruit)

Expected output:

apple
banana
cherry

Write a nested loop to create a multiplication table for numbers 1 to 3.

for i in range(1, 4):
    for j in range(1, 4):
        print(f"{i} * {j} = {i*j}")
    print()  # Print a newline after each inner loop

Expected output:

Exercise 3: Break and Continue Statements

File: control_structures/break_continue.py

Create a new file called break_continue.py in the control_structures directory and complete the following exercises in this file.

Use a break statement to exit a while loop when a certain condition is met.

count = 0
while True:
    print(count)
    count += 1
    if count >= 5:
        break
print("Loop ended")

Expected output:

0
1
2
3
4
Loop ended

Use a continue statement to skip even numbers in a for loop.

for num in range(1, 6):
    if num % 2 == 0:
        continue
    print(num)

Expected output:

1
3
5

Write a loop that searches for a specific number in a list and stops when it's found.

numbers = [4, 2, 7, 1, 8, 3, 6]
search_for = 8

for num in numbers:
    if num == search_for:
        print(f"Found {search_for}!")
        break
    print(f"Not {search_for}...")

Expected output:

Not 8...
Not 8...
Not 8...
Not 8...
Found 8!

Implement a simple number guessing game using a while loop and break statement.

import random

secret_number = random.randint(1, 10)
attempts = 0

while True:
    guess = int(input("Guess the number (1-10): "))
    attempts += 1

    if guess == secret_number:
        print(f"Congratulations! You guessed it in {attempts} attempts.")
        break
    elif guess < secret_number:
        print("Too low. Try again.")
    else:
        print("Too high. Try again.")

Sample run:

Guess the number (1-10): 5
Too low. Try again.
Guess the number (1-10): 8
Too high. Try again.
Guess the number (1-10): 7
Congratulations! You guessed it in 3 attempts.

Use a for loop with else to check if a number is prime.

def is_prime(n):
    if n < 2:
        return False
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            return False
    return True

number = 17
if is_prime(number):
    print(f"{number} is prime.")
else:
    print(f"{number} is not prime.")

Expected output: 17 is prime.

Congratulations!

Remember to run each file separately to see the output of your exercises. You can do this by navigating to the appropriate directory in your terminal and running python filename.py (e.g., python conditionals.py).