01_setup.md

🐍 01 – Setup & First Program

🎯 What You'll Learn

• Install Python and verify it works
• Understand the REPL (interactive shell)
• Write and run your first Python script
• Know the difference between running JS and Python

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📌 JS vs Python — Side by Side

Task	JavaScript (Node)	Python
Check version	node --version	python3 --version
Run a file	node app.js	python3 hello.py
Print output	console.log("Hi")	print("Hi")
Interactive shell	node	python3
Exit shell	.exit or Ctrl+C	exit() or Ctrl+D
Package manager	npm	pip
File extension	.js	.py

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💡 Installing Python

Download from https://python.org — always install Python 3.10 or newer.

# Verify installation
python3 --version
# Python 3.12.0

pip3 --version
# pip 23.x

Windows users: Check "Add Python to PATH" during installation.

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💡 Your First Program

JavaScript

// hello.js
console.log("Hello, World!");
console.log("My name is Ahmed");

node hello.js
# Hello, World!
# My name is Ahmed

Python

# hello.py
print("Hello, World!")
print("My name is Ahmed")

python3 hello.py
# Hello, World!
# My name is Ahmed

Key difference: print() replaces console.log(). No semicolons. No curly braces.

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💡 The REPL (Interactive Shell)

The REPL lets you type Python and see results immediately — perfect for experimenting.

JavaScript REPL

$ node
> 2 + 2
4
> "hello".toUpperCase()
'HELLO'
> .exit

Python REPL

$ python3
>>> 2 + 2
4
>>> "hello".upper()
'HELLO'
>>> exit()

The >>> is Python's prompt. Each line runs immediately.

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💡 Running Python Files

# Create a file
touch hello.py

# Run it
python3 hello.py

# Run with output
python3 -c "print('Hello from command line')"

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💡 Recommended Setup

VS Code
  └── Python extension (ms-python.python)
      ├── IntelliSense (autocomplete)
      ├── Linting (catches errors)
      └── Debugger (breakpoints)

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🧪 Practice

# Try this in your REPL or a file
print("Hello, World!")
print(2 + 2)
print(10 * 5)
print("Ahmed" + " " + "Bro")
print(type(42))
print(type("hello"))

Expected output:

Hello, World!
4
50
Ahmed Bro
<class 'int'>
<class 'str'>

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⚠️ Common Mistakes

Mistake	Wrong	Right
Using JS syntax	console.log("hi")	print("hi")
Adding semicolons	print("hi");	print("hi")
Wrong command	python hello.py	python3 hello.py
Python 2	python --version → 2.7	Must be 3.x

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🔗 Next Lesson

👉 02 – Variables & Data Types