Lesson 3: Running Your First Python Program

It’s time for the "Hello, World!" moment! In this lesson, we will move past the theory and actually run our first independent Python script. By the end of this page, you’ll know how to create a file, write code in it, and see that code come to life in the terminal.

Lesson Overview

In this lesson, we will:

Create a Python File: Learning the .py extension.
Write Your Code: Using VS Code to write instructions.
Run via Terminal: Executing your script like a pro.
Fixing Mistakes: Understanding what happens when things go wrong.

Step 1: Create a Project Folder

Before we write code, we need a place to store it.

Create a folder on your computer named PythonBasics.
Open VS Code.
Go to File > Open Folder... and select your PythonBasics folder.
You should now see the folder name in the sidebar on the left.

Step 2: Create Your First File

All Python files must end with the extension .py. This tells the computer: "Hey, I'm a Python script!"

Click the New File icon next to your folder name in the VS Code sidebar.
Name the file hello.py.
The file will open in the main editor window.

Step 3: Write Your Code

Type the following code into hello.py:

# This is my first Python program!
print("Success! I am now a Python programmer.")

What do those lines mean?

#: This is a Comment. Anything after a # is ignored by Python. It’s a note for you (the human).
print(): The command that shows text on the screen.
"Success!...": The text we want to display.

Don't forget to save! (Press Ctrl+S on Windows or Cmd+S on Mac).

Step 4: Run Your Program

There are two ways to run Python in VS Code:

The "Easy Way" (Play Button):

Look at the top-right corner of your editor. Click the Play Icon (a small triangle).

The "Pro Way" (The Terminal):

Go to Terminal > New Terminal.
In the terminal window at the bottom, type:
```
python hello.py
```
(Or python3 hello.py on macOS).

Output:

Success! I am now a Python programmer.

If you see that text, congratulations! You just successfully executed a Python program.

Step 5: What If it Breaks? (Debugging)

Let's try to break it on purpose. Remove the closing ) at the end of your print statement and try to run it.

# Broken Code
print("Hello"

Result: You will see a SyntaxError. This is Python’s way of saying: "I don't understand your grammar!"

How to fix it:

Read the error message—it usually points to the line number.
Add the ) back.
Save and run again.

Practice Exercise

Create a new file named about_me.py.
Write three separate print statements in it:
- One for your name.
- One for your city.
- One for the year you started learning Python.
Run the file and ensure all three lines appear in the terminal.

Quick Knowledge Check

What file extension do all Python files use?
What does the # symbol represent in Python?
Where do you see the output of your program in VS Code?
What is a SyntaxError?

Key Takeaways

Python files end in .py.
Comments are used to explain code and are ignored by the computer.
Saving your file is required before you can run the latest changes.
Errors are normal—they are just clues to help you fix your logic.

What’s Next?

Now that you can run programs, let's learn how to make them "smart." In Lesson 4, we’ll explore Variables and Data Types—the way programs store and remember information!