Python Programming for Lazy Beginners: A Simple and Easy Tutorial

CHAPTER 5

Flow Control:  Because Even Lazy Programmers Need Some Order

"Flow control is the conductor that guides the symphony of code, bringing harmony and order to the chaotic melodies of programming." — Unknown

Have you ever wondered how your computer knows what to do, and in what order to do it? The answer lies in the art of flow control, the topic of Chapter 5.

Flow control is the programmer's tool for keeping order and structure in their code. It's the technique that allows programs to make decisions, execute certain actions, and repeat processes until certain conditions are met. In this chapter, you'll learn how to use flow control structures like if-else statements, loops, and functions to make your programs more efficient, dynamic, and, most importantly, functional.

Whether you're a seasoned programmer or a newcomer to the world of coding, you'll find something useful in this chapter. Lazy programmers will appreciate the simplicity and efficiency of flow control, while detail-oriented programmers will love the precision and flexibility it provides.

So, sit back, relax, and let the power of flow control take over. With the knowledge you'll gain from this chapter, you'll be able to direct your programs with ease, and even the laziest of programmers will find order in their code.

In Python, the if, elif, and else statements are used to make decisions based on conditions. They work like a choose-your-own-adventure book: you start with an initial question or statement, and then depending on the answer or condition, you move on to the next statement or question.

For example, imagine you are reading a book where you have to decide what to do based on certain conditions. The book might say something like:

"If you want to take the left path, turn to page 10. If you want to take the right path, turn to page 15. If you want to go straight, turn to page 20."

This is similar to how if, elif, and else statements work in Python. You start with an if statement that asks a question or checks a condition. If the answer or condition is true, you move on to the next statement or question. If the answer or condition is false, you move on to the next elif statement or the else statement.

For example, let's say you're writing a program that asks the user to enter their age and then prints a message depending on their age. Here's how it might look:

age = int(input("How old are you? "))

if age < 18:
    print("Sorry, you're not old enough to vote yet.")
elif age >= 18 and age < 21:
    print("You can vote, but you can't drink yet.")
else:
    print("You can vote and drink legally. Cheers!")

In this example, the if statement checks whether the user's age is less than 18. If it is, the program prints a message saying that they're not old enough to vote yet. If the user's age is not less than 18, the program moves on to the elif statement. This statement checks whether the user's age is between 18 and 21 (inclusive). If it is, the program prints a message saying that they can vote but can't drink yet. Finally, if neither of the previous conditions is true (i.e., the user is 21 or older), the program moves on to the else statement and prints a message saying that they can vote and drink legally.

Nested if

Nested if statements are a way of checking multiple conditions in a hierarchical way. It's like a set of Russian dolls, with one nested inside the other. Here's a creative analogy to help you understand: