Question 1

What are decorators in Python?

Accepted Answer

**Target Audience:** Python beginners who have written functions, up to candidates preparing for mid-level interviews
**Difficulty:** Medium
**Python version:** behaviour checked on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime)

> **How to read this doc:** Every idea is first explained in plain words. When a term has a precise name an interviewer expects to hear, it is introduced as a 📌 **Interview term** callout. The Quick Glossary at the end lists all of them.

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Question 2

What is the difference between classmethod and staticmethod?

Accepted Answer

**Target Audience:** Beginners who know what `self` is, up to intermediate developers preparing for Python interviews.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11 and 3.13 (identical output except where a version is named); every in-page example also runs on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Each idea is explained in plain language first. When a word appears that an interviewer expects you to know, it is tagged with `📌 Interview term:

Question 3

What does typing.Self do and why does it beat TypeVar for methods?

Accepted Answer

**Target Audience:** Python developers who write class hierarchies with chainable methods or alternative constructors and use a type checker.
**Difficulty:** Medium
**Python version:** `typing.Self` exists from Python 3.11. Runtime behaviour checked on CPython 3.11.17 and in the page runner (Pyodide 0.25.1, CPython 3.11.3). Type-checker output is from mypy 2.3.1 with `--python-version 3.11`.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interv

Question 4

What is the descriptor protocol?

Accepted Answer

**Target Audience:** Intermediate Python developers who use `@property` and methods every day and want to know the machinery under them.
**Difficulty:** Hard
**Python version:** Behaviour checked on CPython 3.11 (outputs identical on 3.12 and 3.13); both examples also run in the page on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Plain-language explanation comes first. The vocabulary an interviewer expects is tagged `📌 Interview term:` and defined on the spot; all terms are co

Question 5

What is __init_subclass__ in Python?

Accepted Answer

**Target Audience:** Intermediate Python developers comfortable with classes and inheritance who have heard of metaclasses and want the simpler tool.
**Difficulty:** Hard
**Python version:** Behaviour checked on CPython 3.11 (outputs identical on 3.12 and 3.13); both examples also run in the page on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Ideas come in plain language first. Terms an interviewer expects you to use are tagged `📌 Interview term:` and defined where they appear

PYTHONDECODED.

Medium

What are decorators in Python?

What is the difference between classmethod and staticmethod?

What does typing.Self do and why does it beat TypeVar for methods?

Hard

What is the descriptor protocol?

What is __init_subclass__ in Python?