Python for non-Programmers Ep.3

Making Decisions: If Statements and Loops

Welcome back to our Python adventure! 🐍

Do you want to make decision in the code? Today we’ll learn how to make your programs think and repeat actions automatically.

So far, we’ve covered variables and basic operations. But what makes programming truly powerful is the ability to create logic—making your code decide what to do based on different situations.

Photo by Kelly Sikkema on Unsplash

Before We Start

Make sure you have your Python environment ready from our first episode. If you need a refresher on where to practice, check back here → Episode 1

Today we’re diving into two fundamental concepts that will transform your Python skills: conditional statements (if/else) and loops (for/while).

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The Art of Decision Making: If Statements

Programming is essentially about making decisions. Should I do this or that? Should I repeat this action? Should I stop here?

In Python, we use if statements to create this decision-making logic.

Let’s start with the basic structure:

if condition:
    # do this
else:
    # do that instead

Notice something crucial: Python uses indentation to group code together. This is different from many other programming languages!

What is indentation? It’s the empty space at the beginning of a line. In Python, you create this space by pressing the Tab key once at the start of each line that belongs to your if statement.

if age >= 18:
    print(”You can vote!”)  # ← This line starts with a Tab
    print(”Welcome to democracy!”)  # ← This line also starts with a Tab
else:
    print(”Too young to vote”)  # ← This line starts with a Tab too

Important rule: All lines that belong to the same block must have the same indentation. Python will give you an error if the indentation is inconsistent.

Your First Decision

Let’s try a simple example:

age = 25

if age >= 18:
    print(”You can vote!”)
else:
    print(”Too young to vote”)

Here’s what happens:

• Python checks if the variable age is greater than or equal to 18

• If true, it prints “You can vote!”

• If false, it prints “Too young to vote”

Multiple Conditions with elif

Sometimes you need more than just two options. Enter elif (short for “else if”):

temperature = 22

if temperature > 30:
    print(”It’s hot outside!”)
elif temperature > 15:
    print(”Perfect weather”)
else:
    print(”Bring a jacket”)

This creates a chain of decisions that Python checks in order, stopping at the first true condition.

Photo by Fatos Bytyqi on Unsplash

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The Power of Repetition: Loops

What if you want your program to repeat an action multiple times? That’s where loops come in.

Python has two main types of loops: for loops and while loops.

For Loops: When You Know How Many Times

A for loop is perfect when you know exactly how many times you want to repeat something.

# Count from 1 to 10
for i in range(1, 11):
    print(f”Number: {i}”)  # ← Notice the Tab indentation here

The range(1, 11) function creates numbers from 1 to 10 (notice that 11 is excluded—Python stops before the end number).

What’s that f”{}” thing? This is called an f-string (formatted string), and it’s one of Python’s coolest features!

Instead of writing:

print(”Number: “ + str(i))  # Old, complicated way

You can write:

print(f”Number: {i}”)  # New, elegant way

The f before the quotes tells Python this is a formatted string. Inside the curly braces {}, you can put any variable, and Python will automatically convert it to text and insert it into the string.

More f-string examples:

name = “Alice”
age = 25
print(f”Hello {name}, you are {age} years old”)
# Prints: Hello Alice, you are 25 years old

price = 19.99
print(f”The item costs ${price}”)
# Prints: The item costs $19.99

Here’s another example:

# Print each character in a string
name = “Python”
for letter in name:
    print(f”Letter: {letter}”)  # ← Tab indentation + f-string magic!

While Loops: When You Don’t Know When to Stop

A while loop continues as long as a condition remains true:

countdown = 5

while countdown > 0:
    print(f”Countdown: {countdown}”)  # ← Tab + f-string
    countdown = countdown - 1  # ← Tab indentation. Decreasing by 1 the counter

print(”Blast off! 🚀”)  # ← Back to no indentation (outside the loop)

Important: Make sure your while loop has a way to eventually become false, otherwise it will run forever and I am pretty sure your laptop won’t approve!

Photo by Roman Synkevych on Unsplash

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Putting It All Together: Our Exercise

Let’s create a program that determines if a number is even or odd:

# Get a number (we’ll use a variable for now)
number = 42

if number % 2 == 0:
    print(f”{number} is even”)
else:
    print(f”{number} is odd”)

The % operator gives you the remainder after division. If dividing by 2 gives no remainder (== 0), the number is even.

Let’s make it more interesting by checking multiple numbers:

# Check numbers from 1 to 10
for num in range(1, 11):
    if num % 2 == 0:
        print(f”{num} is even”)
    else:
        print(f”{num} is odd”)

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Pro Tips

Indentation Matters: Python uses indentation instead of curly braces like other languages. Make sure your indented blocks are consistent (use either spaces or tabs, not both).

Testing Conditions: You can use various comparison operators:

• == (equal to)

• != (not equal to)

• > (greater than)

• < (less than)

• >= (greater than or equal)

• <= (less than or equal)

Combining Conditions: Use and and or to combine multiple conditions:

age = 20
has_license = True

if age >= 18 and has_license:
    print(”You can drive!”)

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Your Challenge

Try creating a program that:

1. Uses an if statement to check something

2. Uses an else statement for the alternative

3. Includes at least one loop (either for or while)

For example, you could create a program that counts from 1 to 20 and prints “Fizz” for even numbers and “Buzz” for odd numbers.

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Wrap-up

Today you’ve learned the foundation of programming logic:

✅ If statements → Making decisions in your code

✅ Elif and else → Handling multiple conditions

✅ For loops → Repeating actions a specific number of times

✅ While loops → Repeating until a condition changes

These tools let your programs become truly interactive and intelligent. In the next episode, we’ll explore how to get input from users and make our programs even more dynamic.

Keep practicing, and remember: every expert programmer started exactly where you are now! 🚀

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Final Reminder: Use the # symbol to add comments to your code as you experiment. It helps you remember what each part does and makes learning much easier.

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I know we’ve dove quite a lot in this short series until now, especially if you haven’t ever tried this tool before. For this reason, I will try to create kind of an “exercise-post” next week to help you fix the concepts in your mind.

Let me know if you like the idea 💡