Question 1

What are mixins in Python?

Accepted Answer

**Target Audience:** Developers who know single inheritance and want to use (and explain) multiple inheritance the way Python libraries do.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11.17, 3.12 and 3.13, and in the page runner (Pyodide 0.25.1, CPython 3.11.3).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. All output shown was produced by

Question 2

What is the difference between an iterable and an iterator?

Accepted Answer

**Target Audience:** Python developers who loop over things every day and want the precise model behind it
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); the protocol is the same on 3.12 and 3.13

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. Every output block in the **Verified** section wa

Question 3

What is the difference between bytes and str?

Accepted Answer

**Target Audience:** Python developers who handle files, network data or APIs, explained from zero
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11 (and in the page's Pyodide 3.11 runtime)

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. Every output block in the **Verified** section was copied from a real run of the examples on this page.

## 1.

Question 4

What is composition versus inheritance?

Accepted Answer

**Target Audience:** Developers who can write classes and subclasses and want to know how to choose between the two main ways of reusing code.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11.17, 3.12 and 3.13, and in the page runner (Pyodide 0.25.1, CPython 3.11.3).

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact words an interviewer expects. All output shown was produced

Question 5

What useful types does the collections module provide?

Accepted Answer

**Target Audience:** Python learners who know `list` and `dict` and want the tools that make everyday code shorter, up to candidates who need the gotchas and internals.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime, which is CPython 3.11.3).

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. Ever

Question 6

What are abstract base classes and Protocols?

Accepted Answer

**Target Audience:** Developers who know classes and inheritance and have seen `ABC` or `Protocol` in a codebase, up to candidates who need to compare nominal and structural typing precisely.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime, which is CPython 3.11.3); the differences we saw on 3.12 and 3.13 are called out.

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

Question 7

What is a metaclass?

Accepted Answer

**Target Audience:** Python developers who are comfortable with classes and want to know what sits one level above them
**Difficulty:** Hard
**Python version:** Checked on CPython 3.11, 3.12 and 3.13 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); the hook order is identical on all of them

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact word an interviewer expects. Every output block in

PYTHONDECODED.

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