Intorduction

Python is a high-level, easy-to-read programming language created by Guido van Rossum in 1991.

It is used for:

• 🌐 Web development
• 📊 Data analysis
• 🤖 Artificial Intelligence & Machine Learning
• 🎮 Game development
• 🖥️ Automation & scripting
• 📱 App development

Python is popular because:

• It has simple syntax (easy to read like English)
• It has a large community
• It works on Windows, Mac, and Linux
• It has thousands of ready-made libraries

Installing Python

To start coding:

1. Go to the official website:
2. 👉 Python Software Foundation
3. Download Python for your operating system.
4. Install it.
5. During installation, check ✅ "Add Python to PATH".

After installing, open Command Prompt (Windows) or Terminal (Mac/Linux) and type:

python --version

If installed correctly, it will show something like:

Python 3.12.1

Writing Your First Python Program

The traditional first program is "Hello, World!"

print("Hello, World!")

Explanation:

• print() → Displays output on the screen
• "Hello, World!" → Text (called a string)

Python Syntax Basics

Python is indentation-based (spaces matter!).

Example:

if 5 > 2:
    print("Five is greater than two")

Notice the space before print() — that indentation is required.

Variables in Python

Variables store data.

name = "Alice"
age = 25
height = 5.6
is_student = True

Variable Rules:

• No spaces in variable names
• Cannot start with a number
• Case-sensitive (age ≠ Age)

Data Types in Python

Here are the main data types:

| Data Type | Example | Description |
|-----------|----------|------------|
| int | 10 | Whole numbers |
| float | 3.14 | Decimal numbers |
| str | "Hello" | Text |
| bool | True / False | Boolean values |
| list | [1, 2, 3] | Collection (changeable) |
| tuple | (1, 2, 3) | Collection (unchangeable) |
| dict | {"name": "Alice"} | Key-value pairs |

Example:

x = 10              # int
y = 3.14            # float
name = "John"       # string
is_valid = False    # boolean

Taking User Input

name = input("Enter your name: ")
print("Hello", name)

⚠️ Important: input() always returns a string.

If you want a number:

age = int(input("Enter your age: "))
print("You are", age, "years old.")

Operators in Python

| Type | Operators | Example |
|------|-----------|----------|
| Arithmetic | + - * / % | 5 + 2 |
| Comparison | == != > < >= <= | 5 > 3 |
| Logical | and or not | x > 5 and x < 10 |

Example:

a = 10
b = 5

print(a + b)
print(a > b)

Conditional Statements (if-else)

Used for decision making.

age = 18

if age >= 18:
    print("You are an adult")
else:
    print("You are a minor")

With elif:

score = 85

if score >= 90:
    print("Grade A")
elif score >= 80:
    print("Grade B")
else:
    print("Grade C")

Loops in Python

1. For Loop

for i in range(5):
    print(i)

Output:

0
1
2
3
4

2. While Loop

count = 0

while count < 5:
    print(count)
    count += 1

Functions in Python

Functions let you reuse code.

def greet(name):
    print("Hello", name)

greet("Alice")

Function with return value:

def add(a, b):
    return a + b

result = add(5, 3)
print(result)

Lists in Python

Lists store multiple values.

fruits = ["apple", "banana", "cherry"]

print(fruits[0])       # Access first item
fruits.append("orange")  # Add item
print(len(fruits))     # Length

Dictionaries in Python

Dictionaries store key-value pairs.

student = {
    "name": "John",
    "age": 20,
    "course": "Computer Science"
}

print(student["name"])

Python Libraries

One of Python’s biggest strengths is its libraries.

Examples:

• math → Mathematics
• random → Random numbers
• datetime → Dates & time

Example:

import random

print(random.randint(1, 10))

Comments in Python

Comments are ignored by Python.

# This is a comment

"""
This is a
multi-line comment
"""

Why Learn Python?

Python is used by major companies like:

• Google
• Netflix
• Instagram
• Spotify

It is also heavily used in:

• Data Science
• Machine Learning
• Automation
• Web Development