The power of Special Methods in Python. Make better classes!

Explore how the Python data model lets objects emulate built-in types through special methods, including dunder methods, enabling len, iteration, for-loops, and context management.

Learn to implement __repr__ and __str__ with an employee class to show how print uses __str__, how defaults reveal memory addresses, and how __repr__ supports debugging and recreating objects.

Discover how Python assigns a unique, read-only identity to every object, how the is keyword checks shared memory in CPython, and why identity can vary by implementation.

Implement __eq__ to compare objects by employee ID rather than identity. See how Python uses __eq__ in equality checks, and how in and not equals rely on it.

Explore how to implement comparisons in Python by defining __lt__, __le__, __gt__, and __ge__ to compare magnitudes and support sorting, including using sorted to sort files by type and name.

Explore how the __hash__ method powers hash tables like Python's dictionary, distinguishes hash from equality, and explains collisions, salted string hashes, and the rule that hash must not change.

Learn how Python performs object instantiation and constructors, including __new__ and __init__, how to require arguments, and how to override constructors in subclasses using super.

Explore the power of special methods in Python by making a factory class callable, enabling a single create_user_image method to produce user images with a database connection.

Learn to make your object behave like lists by implementing __len__ and supporting the built-in len function, illustrated with a todolist class and its items.

Learn how to use special methods in Python to make objects subscriptable by implementing __getitem__ and __setitem__, use len and slices, and design simple dictionaries with custom item access.

Compare subscription with iteration by building a range-like class that implements __iter__ and __next__, using iter and next to yield values until StopIteration. Preview operator overloading in the next chapter.

Overload arithmetic operators in Python by implementing __add__ and __mul__ in a Vector2 class, returning new vectors and handling scalar multiplication correctly.

Explore how a context manager and the with statement automate resource management, using __enter__ and __exit__ to safely open and close files, databases, and logs—even after errors.

Explore how Python evaluates truth using the __bool__ method, with __len__ as a fallback, and how truthy and falsy values affect if statements.

Suppress special methods in Python by setting __hash__ to None and triggering type errors, then review a subset of methods, attributes, and terminology around dunder, magic, and the data model.

Explore how to make your classes emulate built-in types using Python's special methods, map built-in functions and operators to dunder methods, and implement containers and context managers.