Python 3 Complete Guide: Core Syntax, Data Structures & Best Practices

By Marcus Sterling • Beginner • 16 min read • Updated 2026-09-11

What You Will Master in This Tutorial

Master foundational syntax: control flow, truthy/falsy evaluation, and string formatting.
Understand mutable vs. immutable types (lists, tuples, dicts, sets).
Write modular, reusable functions with type annotations and docstrings.

1. Pythonic Syntax and Type Annotations

Python emphasizes readability. Modern Python 3.12+ makes extensive use of type hinting to improve IDE autocomplete and eliminate runtime type errors.

PYTHON

from typing import List

def calculate_discount(prices: List[float], discount_rate: float = 0.10) -> float:
    if not 0 <= discount_rate <= 1:
        raise ValueError("Discount rate must be between 0.0 and 1.0")
    subtotal = sum(prices)
    return round(subtotal * (1 - discount_rate), 2)

Note: Use modern type annotations (PEP 484/585) so tools like MyPy catch bugs before production.

Knowledge Check: Test Your Understanding

1. Which of the following data types is immutable in Python?

Frequently Asked Questions

Why should I use virtual environments in Python?

Virtual environments isolate package dependencies per project, preventing conflicts across your system.