Python
Abstract Base Classes and Interfaces
An abstract base class states what subclasses must implement, and refuses to let an incomplete one be created. It is how Python enforces a contract.
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Python
Multiple Inheritance and the MRO
A class can inherit from several parents. The method resolution order decides which version wins, and C3 linearisation is the algorithm that computes...
Python
Composition, Delegation and Design Choices
Inheritance says "is a"; composition says "has a". Most of the time the honest answer is "has a", and the resulting design is easier to change.
Python
Iterables and Iterators
An iterable can produce an iterator; an iterator produces one value at a time and remembers where it is. Every for loop in Python is built on those tw...
Python
Generators and yield
A generator function produces values one at a time and pauses between them, keeping all its local state. It is the easiest way to write an iterator an...
Python
Lazy Evaluation and Streaming Data
Lazy means computing a value only when it is asked for. Python uses it throughout, and using it deliberately is what makes a program handle data large...
Python
Decorators: Wrapping Functions
A decorator takes a function, wraps it in another function, and gives the wrapper the original name. The @ symbol is shorthand for exactly that.
Python
Practical Decorator Patterns
Registries, access control, deprecation, rate limiting and instrumentation - the decorator shapes that appear in real codebases, and how to test them.
Python
Context Managers and the with Statement
A context manager guarantees that setup and cleanup both happen, whatever occurs in between. with is how you use one, and two methods are all it takes...
Python
Descriptors: The Machinery Behind Attributes
A descriptor is an object that controls what happens when an attribute is read, written or deleted. property, methods, classmethod and staticmethod ar...
Python
Dataclasses
A dataclass generates __init__, __repr__ and __eq__ from field declarations. It removes the boilerplate from every class whose main job is holding dat...
Python
Objects, References and Identity
Everything in Python is an object with a type, an identity and a value. Names are labels bound to objects, and almost every surprising behaviour follo...