CHAPTER 3 — YOUR FIRST PYTHON PROGRAM

CHAPTER 3 — YOUR FIRST PYTHON PROGRAM - Printable Version

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CHAPTER 3 — YOUR FIRST PYTHON PROGRAM - Leejohnston - 11-15-2025

Chapter 3 — Your First Python Program
Where you officially become a programmer

In this chapter, you will:
• write your first real Python program
• run it
• understand exactly what the computer is doing
• learn the rules of Python’s “grammar”

This is where everything begins.

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3.1 Creating Your First Python File

Open VS Code.

1. Click File → New File
2. Save it immediately as:

hello.py

(Every Python file ends with .py)

Your editor is now ready for code.

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3.2 The First Line Every Beginner Writes

Type this:

Code:
print("Hello, world!")

This is the traditional first program across the entire world.

Now run it:

VS Code:
• Press the “Run Python File” button
OR
Terminal:

Code:
python hello.py

You should see:

Hello, world!

You have now written a real, valid Python program.

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3.3 How the Program Works (Explained Simply)

Python reads your file from top to bottom.

The print command tells the computer:
“Display whatever is inside the brackets.”

Like this:

Code:
print("Hello!")  # prints Hello!

Anything inside quotation marks is text (called a string).

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3.4 Python Grammar — Very Simple Rules

Python has a very clean language structure.

Here are the essential rules you need right now:

Rule 1: Every instruction goes on its own line.

Code:
print("A")

print("B")

Rule 2: Text must be inside quotation marks.

Code:
print("This is text")

Rule 3: Python is case-sensitive.
“print” is correct
“Print”, “PRINT”, and “pRint” will NOT work.

Rule 4: Brackets must be matched.

Code:
print("Hello")    # correct

Code:
print("Hello"    # error

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3.5 Adding More Lines

Try this:

Code:
print("This is my first program.")

print("I am learning Python.")

print("It feels easy!")

When you run it, Python prints each line in order.

This is the basic structure of every program:
a list of instructions, executed top to bottom.

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3.6 Adding Comments (Notes to Yourself)

A comment is a line the computer ignores.
It starts with a # symbol.

Code:
# This is a comment

print("This will run")

# This won't run: print("Secret code")

Programmers use comments to explain what their code does.

You will use comments in your exercises and projects.

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3.7 Exercise — Write a Mini Program

Create a file called intro.py
Write a program that displays:

• your name
• your favourite number
• your favourite hobby
• a positive message

Example structure:

Code:
print("My name is ...")

print("My favourite number is ...")

print("I enjoy ...")

print("Today is a great day!")

Run the file to see your results.

(This exercise builds confidence and helps you understand the basics.)

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3.8 Small Challenge

Try writing a program that prints:

1. A sentence on one line
2. A second sentence
3. A blank line
4. Two more sentences

Hint: A blank line is just:

Code:
print("")

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3.9 Chapter Summary

• You created your first Python file
• You wrote your first real program
• You learned how print() works
• You learned Python’s simple rules
• You learned what comments are
• You wrote your first mini project

Next, we level up to:
Chapter 4 — Variables & Data Types

This is where you start storing information and building real logic.

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Written and Compiled by Lee Johnston — Founder of The Lumin Archive