Introduction to Python. Setup and First Program

Python is a modern high-level programming language created by Guido van Rossum in 1991. The name comes from the comedy show "Monty Python's Flying Circus," but the language itself is serious and powerful.

Why is Python so popular?

1. Readability: Python code reads almost like English
2. Versatility: Python is used for:

• Web development (Django, Flask)
• Scientific computing (Data Science, AI)
• Task automation
• Game development
• Working with data

1. Large community: Millions of developers worldwide
2. Free: Python is completely free and open source

Where is Python used?

• YouTube, Instagram, Spotify - built with Python
• Google, NASA, Netflix - use Python
• Artificial intelligence and machine learning
• Automation and scripting

Step 1: Download Python

1. Go to the official website: https://www.python.org/downloads/
2. Download the latest Python 3.x version (3.11 or newer recommended)
3. During installation, make sure to check "Add Python to PATH"

Step 2: Verify the installation

Open Command Prompt (Windows) or Terminal (Mac/Linux) and enter:

python --version

Or:

python3 --version

You should see something like: Python 3.11.5

Step 3: Install a code editor

Recommended editors:

• VS Code (Visual Studio Code) - free and popular
• PyCharm - a powerful IDE for Python
• Sublime Text - lightweight and fast

For beginners, we recommend VS Code.

A programming tradition is to start with a program that prints "Hello, World!". This is the simplest program that confirms everything works correctly.

Creating the file:

1. Open your code editor
2. Create a new file named hello.py
3. Write the following code:

print("Hello, World!")

Save the file

Running the program:

Option 1: From the command line

python hello.py

Option 2: In VS Code

• Right-click the file
• Select "Run Python File in Terminal"

Result:

You will see in the terminal:

Hello, World!

Congratulations! You have written your first Python program!

Python has an interactive mode (REPL - Read-Eval-Print Loop) where you can run code immediately without creating files.

Starting interactive mode:

Open the command line and enter:

python

Or:

python3

You will see something like:

Python 3.11.5 (main, ...)
Type "help", "copyright", "credits" or "license" for more information.
>>>

The >>> symbol is a prompt showing that Python is ready to accept commands.

Usage examples:

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

>>> 2 + 2
4

>>> print("This is my first Python code!")
This is my first Python code!

Exiting interactive mode:

Enter:

>>> exit()

Or press Ctrl+Z (Windows) or Ctrl+D (Mac/Linux)

When to use interactive mode:

• Quick code testing
• Experimenting with Python
• Learning and exploration

When to use files:

• Building real programs
• Saving code for later use
• Projects you need to run many times

Let's look at the basic structure of a Python program:

# This is a comment - Python ignores everything after the # symbol

# Importing modules (we will cover this in more detail later)
import math

# Comments explain the code
# This is just an example of program structure

# Running code
print("Hello! This is my first Python program")

# Simple output
print("Python is a great programming language!")

Key points:

1. Comments start with # - they help explain the code
2. The print() function displays information on the screen
3. Code runs from top to bottom, line by line

Code style:

Python follows the philosophy that "beautiful code is readable code." It is important to:

• Use indentation (4 spaces)
• Write clear code
• Add comments where needed