Chapter Review and Practice Problems | Control Flow: Making Decisions and Repeating Actions | Your First Steps in Python: A Beginner to Intermediate Guide

Congratulations on reaching the end of our chapter on Control Flow! You've learned how to make your Python programs dynamic by controlling the order in which statements are executed. We've explored the power of conditional statements (if, elif, else) to make decisions based on whether certain conditions are true or false. We've also delved into loops (for and while) to efficiently repeat actions multiple times. Mastering these concepts is a significant step towards writing more complex and intelligent programs.

Let's quickly recap the key takeaways from this chapter:

if, elif, else Statements: These allow your program to execute different blocks of code based on boolean conditions. Remember that indentation is crucial in Python to define these blocks.

graph TD
    A[Start]
    B{Condition Met?}
    C[Execute if Block]
    D[Execute elif Block]
    E[Execute else Block]
    F[Continue Program]

    A --> B
    B -- Yes --> C
    B -- No --> G{Another Condition?}
    G -- Yes --> D
    G -- No --> H{No Conditions Met?}
    H -- Yes --> E
    H -- No --> F
    C --> F
    D --> F
    E --> F

for Loops: Ideal for iterating over a sequence (like a list, tuple, string, or range) and executing a block of code for each item in the sequence.

for item in sequence:
    # do something with item

while Loops: Useful when you want to repeat a block of code as long as a specific condition remains true. Be mindful of creating infinite loops by ensuring the condition eventually becomes false.

while condition:
    # do something
    # update condition to eventually be false

Loop Control Statements: break allows you to exit a loop prematurely, and continue skips the rest of the current iteration and moves to the next one.

Now, it's time to put your knowledge into practice! The following problems are designed to reinforce your understanding of control flow. Don't be afraid to experiment and refer back to the chapter's examples if you get stuck.

Practice Problems:

Temperature Converter: Write a program that takes a temperature in Celsius as input from the user and converts it to Fahrenheit. Use an if-elif-else structure to provide a message based on the temperature (e.g., 'Freezing', 'Cold', 'Warm', 'Hot'). The formula for Celsius to Fahrenheit is: $F = (C * 9/5) + 32$ .

# Example placeholder for your code
celsius = float(input('Enter temperature in Celsius: '))

# Your if-elif-else logic here

print(f'{celsius} Celsius is {fahrenheit} Fahrenheit.')

Number Guessing Game: Create a simple number guessing game. The program should generate a random integer between 1 and 100 (you'll need to import random). The user then has to guess the number. The program should tell them if their guess is too high, too low, or correct. The game should continue until the user guesses the correct number. Use a while loop and potentially if-elif-else statements.

import random

secret_number = random.randint(1, 100)
guesses = 0

while True:
    # Get user input
    # Compare guess to secret_number
    # Provide feedback (too high, too low, correct)
    # Increment guesses
    # Break loop if correct

Prime Number Checker: Write a program that takes an integer as input and determines if it is a prime number. A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself. You can use a for loop to check for divisibility. Remember to handle edge cases like numbers less than or equal to 1.

number = int(input('Enter a number to check if it's prime: '))

# Your logic here using a for loop

Pattern Printer: Use nested for loops to print the following pattern:

(Hint: You'll need one loop for the number of rows and another for the number of stars in each row.)

for i in range(1, 6):
    # Your inner loop here to print stars

Factorial Calculator: Write a program that calculates the factorial of a non-negative integer. The factorial of a non-negative integer $n$ , denoted by $n!$ , is the product of all positive integers less than or equal to $n$ . For example, $5! = 5 * 4 * 3 * 2 * 1 = 120$ . Use a for loop or a while loop. Handle the case where the input is 0 (0! is defined as 1).

num = int(input('Enter a non-negative integer: '))

# Your logic to calculate factorial here

Take your time with these problems. If you encounter difficulties, revisit the relevant sections of this chapter. Understanding control flow is foundational, and the more you practice, the more confident you'll become. Keep up the great work, and get ready for the exciting concepts in the next chapter!

graph TD A[Start] B{Condition Met?} C[Execute if Block] D[Execute elif Block] E[Execute else Block] F[Continue Program] A --> B B -- Yes --> C B -- No --> G{Another Condition?} G -- Yes --> D G -- No --> H{No Conditions Met?} H -- Yes --> E H -- No --> F C --> F D --> F E --> F

import random secret_number = random.randint(1, 100) guesses = 0 while True: # Get user input # Compare guess to secret_number # Provide feedback (too high, too low, correct) # Increment guesses # Break loop if correct