Python is a versatile, high-level programming language that's easy to learn and widely used in web development, data analysis, artificial intelligence, scientific computing, automation, and more. Let’s break down the basics for someone starting fresh.

1. What is Python?

• A high-level programming language created by Guido van Rossum in 1991.

Python is:
• Interpreted: Executes code line-by-line, making it beginner-friendly.
• Open Source: Free to use and distribute, with a large community contributing to its development.
• Dynamically Typed: No need to declare variable types.
• Multi-Paradigm: Supports procedural, object-oriented, and functional programming styles.
• High-Level: Abstracts low-level details, allowing you to focus on problem-solving.
• Readable: Emphasizes code readability, making it easier to understand and maintain.
• Versatile: Used in various fields like web development, data science, and machine learning.
• Portable: Runs on multiple platforms (Windows, macOS, Linux) without modification.

2. Installation of Python on Windows and Linux

To start using Python:

1. Download Python from the official website www.python.org .
2. Choose the version suitable for your operating system (Windows, macOS, Linux).
3. Install Python, ensuring the option "Add Python to PATH" is checked during installation.

3. Verify installation

Verify Installation of python by typing 'python --version' in the terminal or command prompt.

It should display the installed version of Python.

4. Writing Your First Python Program

You can run Python code in:
• Python Shell: Interactive console for running Python commands.
• IDEs: Integrated Development Environments like PyCharm, VSCode, or Jupyter Notebook.
• Script File: Save your code in a .py file and run it using python filename.py.

Hello, World! Example

print("Hello, World..!")

Run the code, and output is: Hello, World..!

5. Python Basics

Variables and Data Types

Variables store data. You don’t need to declare their type.

# Variables
name = "Alice"       # String
age = 25             # Integer
height = 5.7         # Float
is_student = True    # Boolean

print(name, age, height, is_student)

Input and Output

• Input: Get data from the user.
• Output: Display data to the user.

name = input("Enter your name: ")
print(f"Hello, {name}!")

Control Flow

# If-Else Statement

age = int(input("Enter your age: "))
if age >= 18:
    print("You are an adult.")
else:
    print("You are a minor.")

Loops

# For loop

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

# While loop

count = 0
while count < 5:
    print(count)
    count += 1

6. Functions in python

Functions help organize reusable code.

def greet(name):
    return f"Hello, {name}!"

print(greet("Alice"))

7. Data Structures in python

Python provides built-in data structures for organizing data.

Lists: Ordered, mutable collections.

fruits = ["apple", "banana", "cherry"]
fruits.append("orange")
print(fruits)

Tuples: Ordered, immutable collections.

coordinates = (10, 20)
print(coordinates)
•	Dictionaries: Key-value pairs.
person = {"name": "Alice", "age": 25}
print(person["name"])

• Sets: Unordered collections of unique elements.

unique_numbers = {1, 2, 3, 2}
print(unique_numbers)  # Output: {1, 2, 3}

8. Working with Libraries in python

Python’s strength lies in its rich ecosystem of libraries.
• Install Libraries: Use pip (Python's package manager) to install libraries.

pip install numpy

• Example: Using the math Library

import math

print(math.sqrt(16))  # Output: 4.0

9. Error Handling

Python uses try, except, and finally for handling exceptions.

try:
    result = 10 / 0
except ZeroDivisionError:
    print("You can't divide by zero!")
finally:
    print("Execution finished.")

10. File Handling in python

Python makes it easy to work with files.

# Writing to a file

with open("example.txt", "w") as file:
    file.write("Hello, World!")

# Reading from a file

with open("example.txt", "r") as file:
    print(file.read())

11. Object-Oriented Programming

Python supports object-oriented programming (OOP) using classes and objects.

class Car:
    def __init__(self, make, model):
        self.make = make
        self.model = model

    def display_info(self):
        return f"{self.make} {self.model}"

my_car = Car("Toyota", "Corolla")
print(my_car.display_info())  # Output: Toyota Corolla

OOP allows you to create reusable code and model real-world entities.

Example: Creating a Person class

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def introduce(self):
        return f"My name is {self.name}, and I am {self.age} years old."

alice = Person("Alice", 25)
print(alice.introduce())

12. Python Ecosystem

Python’s ecosystem is vast and diverse, with libraries and frameworks catering to various domains. Here are some popular libraries:

• Web Development: Flask, Django
• Data Science: Pandas, NumPy, Matplotlib
• Machine Learning: Scikit-learn, TensorFlow, PyTorch
• Automation: Selenium, PyAutoGUI