01-first-python-program.md

Writing Your First Python Program, Step by Step

Part 1 of the How to Write Code series.

This page shows the shortest possible path from an empty computer to a running program.

What you need

• Python 3.8 or newer installed (check with python --version)
• A text editor (VS Code recommended) or any browser-based Python editor
• About 10 minutes

Step 1 — Create the file

Create a folder called learn-code, then inside it create a file named hello.py.

The .py ending tells the computer the file contains Python code.

Step 2 — Type one line of code

print("Hello, World!")

print() is a built-in function that sends whatever is inside the brackets to the screen. Text must be wrapped in quotes — that is called a string.

Step 3 — Run the file

Open a terminal in the same folder and run:

python hello.py

You should see:

Hello, World!

If you instead see python: command not found, try python3 hello.py (common on macOS and Linux).

Step 4 — Make it interactive

Now accept input from the user:

name = input("What is your name? ")
print(f"Hello, {name}! Welcome to programming.")

Run it:

python hello.py

What is your name? Rita
Hello, Rita! Welcome to programming.

The f"..." prefix creates an f-string, which lets you drop variables directly into text with {}.

Step 5 — Save it to Git

git init
git add hello.py
git commit -m "Add first Python program"

Now your work has a saved history you can return to.

Common first-run errors

Message	Cause	Fix
SyntaxError: invalid syntax	Missing closing quote or bracket	Count your quotes
command not found: python	Python not on PATH	Use python3 instead
FileNotFoundError	Wrong folder	cd into the folder that holds the file

Next step

Continue to Variables, data types and operators.