What is Python? — Python Basics

ANALOGY

Python is the Swiss army knife. JavaScript runs in browsers (its main domain). Python runs everywhere and does everything — write a web server, train a machine learning model, automate file management, analyse a spreadsheet, build a chatbot. No other language has as many production use cases across as many different fields.

Where Python is used

—Web development — Django and Flask power Instagram, Pinterest, Spotify backends
—Data science — pandas, NumPy, matplotlib are the standard data analysis stack
—Machine learning — TensorFlow, PyTorch, and scikit-learn are all Python-first
—Automation — scripts that replace hours of manual work in minutes
—DevOps — Ansible (infrastructure automation) is written in Python

Your first Python program

python

# This is a comment — the # symbol starts a comment
print("Hello, World!")

# Variables — no type declarations needed
name = "Nelson"
age  = 26
pi   = 3.14159

# Python infers the type from the value
print(name)         # Nelson
print(type(name))   # <class 'str'>
print(type(age))    # <class 'int'>

# String formatting — f-strings (the modern way)
print(f"Hello, {name}! You are {age} years old.")

Running Python

bash

# Check version (need Python 3.8+)
python --version    # or python3 --version

# Run a file
python my_script.py

# Interactive REPL
python
>>> print("Hello!")
>>> 2 + 2
4
>>> exit()

# VS Code: install the Python extension, then run with F5