⚙️ Lesson 2: Setting Up Python & Your First Program

📥 Getting Python on Your Computer

Think of Python as a new language your computer needs to learn. Just like you might install a Spanish dictionary app to understand Spanish, you need to install Python for your computer to understand Python code.

Step-by-Step Installation Guide

# Ubuntu/Debian
sudo apt-get install python3

# Fedora
sudo dnf install python3

# Arch
sudo pacman -S python

✅ Verify Your Installation

Let's make sure Python is properly installed:

1. Open Command Prompt (Windows) or Terminal (Mac/Linux)
2. Type: python --version or python3 --version
3. You should see something like: Python 3.12.0
4. If you see an error, try restarting your computer and trying again

✌️ Two Ways to Write Python

You have two main options for writing Python code, like choosing between a calculator and a notebook:

Opening IDLE

1. Look for "IDLE" in your programs (it comes with Python)
2. You'll see a window with >>> — this is Python's way of saying "I'm listening!"

👋 Hello, World! — Your First Program

In programming tradition, the first program everyone writes displays "Hello, World!" It's like a programmer's way of saying "Hi!" to their computer.

>>> print("Hello, World!")
Hello, World!

Let's break this down:

🧮 Python as Your Personal Calculator

Try these in IDLE:

>>> 5 + 3          # Addition
8
>>> 100 - 42       # Subtraction
58
>>> 7 * 6          # Multiplication
42
>>> 20 / 4         # Division (always returns a decimal)
5.0
>>> 2 ** 3         # Exponentiation (2 to the power of 3)
8

🔤 Playing with Text

Python can work with words too!

>>> "Python" + " is" + " fun!"    # Concatenation — joining strings
'Python is fun!'
>>> "Ha" * 5                       # Repetition — repeat a string
'HaHaHaHaHa'
>>> len("Hello")                   # len() counts characters
5

📄 Creating Your First Script File

Now let's save a program so we can run it again later:

Step-by-Step Script Creation

1. Open a text editor (Notepad on Windows, TextEdit on Mac, or IDLE's File → New File)
2. Type this code:

# My first Python script!
# The # symbol creates comments — notes for humans that Python ignores

print("Welcome to Python programming!")
print("Let me do some math for you:")
print("10 + 5 =", 10 + 5)
print("50 * 2 =", 50 * 2)
print()  # Empty print creates a blank line
print("I can work with text too:")
print("Your name backwards is:", "Anna"[::-1])
print("SHOUTING IN CAPS:", "hello".upper())
print("whispering in lowercase:", "HELLO".lower())

Welcome to Python programming!
Let me do some math for you:
10 + 5 = 15
50 * 2 = 100

I can work with text too:
Your name backwards is: annA
SHOUTING IN CAPS: HELLO
whispering in lowercase: hello

3. Save the file as my_first_program.py (the .py tells the computer it's Python)
4. Run it:
   • In IDLE: Press F5 or Run → Run Module
   • In VS Code: Press Ctrl+F5
   • In terminal: python my_first_program.py

⚠️ Important Note: Always save your file with the .py extension. Without it, your computer won't know it's a Python program, and your editor won't give you helpful color-coding (syntax highlighting).

🐛 Understanding Errors — Your New Friends!

Errors aren't bad — they're Python trying to help you! Think of them as a helpful friend saying "Hey, I think you meant something else here."

🏋️ Practice Exercises

>>> 24 * 7          # Hours in a week
168
>>> 5 * 365         # $5/day for a year
1825
>>> 80 * 0.15       # 15% of 80
12.0

>>> "Alice " * 10
'Alice Alice Alice Alice Alice Alice Alice Alice Alice Alice '
>>> "I" + " love" + " Python!"
'I love Python!'
>>> len("Alice Johnson")
13

# My Personal Introduction
print("=== Welcome to My Page! ===")
print("Name: Alice")
print("Favorite number times 10:", 7 * 10)
print("Favorite food:", "pizza".upper())
print("Age in days (approx):", 25 * 365)

=== Welcome to My Page! ===
Name: Alice
Favorite number times 10: 70
Favorite food: PIZZA
Age in days (approx): 9125

Summary

🚀 What's Next?

In our next lesson, we'll learn about variables — Python's way of remembering information. Think of them as labeled boxes where you can store data for later use!