Introduction to Python

What is Python?

Python is a high-level, interpreted programming language known for its simplicity and readability. Created by Guido van Rossum and first released in 1991, Python has become one of the most popular programming languages in the world.

Why Learn Python?

• Easy to Learn: Python has a simple syntax similar to English
• Versatile: Used in web development, data science, AI, automation, and more
• Large Community: Extensive documentation and support
• Cross-Platform: Runs on Windows, macOS, Linux, and more
• High Demand: Python developers are among the highest paid in the industry

Installing Python

To get started with Python, you need to install it on your computer:

1. Visit the official Python website: python.org
2. Download the latest version for your operating system
3. Run the installer and follow the instructions
4. Verify the installation by opening a terminal and typing python --version

Your First Python Program

Let's start with the traditional "Hello, World!" program:

# This is a comment
print("Hello, World!")

Python Syntax Basics

Python uses indentation to define code blocks, unlike other languages that use curly braces:

# Correct indentation
if 5 > 2:
    print("Five is greater than two!")

# Wrong indentation (will cause an error)
if 5 > 2:
print("Five is greater than two!")  # IndentationError

Comments in Python

Comments are used to explain code and are ignored by the interpreter:

# This is a single line comment

"""
This is a multi-line comment
It spans multiple lines
"""

# Comments can also be placed at the end of a line
print("Hello, World!")  # This prints Hello, World!

Python Variables

Variables are containers for storing data values. In Python, you don't need to declare variables before using them:

# Variable assignment
x = 5
y = "Hello, Python"
print(x)
print(y)

Variable Naming Rules

• Variable names must start with a letter or underscore
• Cannot start with a number
• Can only contain alpha-numeric characters and underscores
• Variable names are case-sensitive

# Legal variable names
myvar = "John"
my_var = "John"
_my_var = "John"
myVar = "John"
MYVAR = "John"
myvar2 = "John"

# Illegal variable names
2myvar = "John"
my-var = "John"
my var = "John"

Python Keywords

Python has a set of keywords that are reserved words that cannot be used as variable names:

# Python keywords
False, None, True, and, as, assert, async, await, break, 
class, continue, def, del, elif, else, except, finally, 
for, from, global, if, import, in, is, lambda, nonlocal, 
not, or, pass, raise, return, try, while, with, yield