Question 1

What is the enum module and when should you use it?

Accepted Answer

**Target Audience:** Python beginners and intermediate developers who use strings or numbers as status codes and want to know what `enum` adds
**Difficulty:** Easy
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); differences in 3.12 are called out where we ran 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. Ever

Question 2

How do you read TOML with tomllib in Python 3.11+?

Accepted Answer

**Target Audience:** Python developers who configure apps or tools, explained from zero
**Difficulty:** Easy
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (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.

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Question 3

How do you convert between Python objects and JSON?

Accepted Answer

**Target Audience:** Beginners learning Python, and developers who want the edge cases an interviewer probes
**Difficulty:** Easy
**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

Question 4

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 5

What is structural pattern matching (match/case)?

Accepted Answer

**Target Audience:** Python developers who know `if`/`elif`, lists, dicts and classes and have never used `match`, plus anyone who wants the exact rules an interviewer probes.
**Difficulty:** Medium
**Python version:** `match` needs Python 3.10+. Behaviour and bytecode checked on CPython 3.11 (gotchas re-run on 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. The words an interviewer expects you to use

Question 6

How does Pydantic v2 validation work (BaseModel, field_validator, mode)?

Accepted Answer

**Target Audience:** Python developers who have seen Pydantic models in FastAPI or config code and want to know exactly what runs, in which order, when data is validated.
**Difficulty:** Medium
**Python version:** Pydantic examples verified with pydantic 2.13.5 (pydantic-core 2.46.5) on CPython 3.13. Pydantic is a third-party package, so those two examples are shown as code for the playground; the first example is a standard-library model of the pipeline that runs in the page on Pyodide 0.25.1 (

Question 7

What are common Python security pitfalls?

Accepted Answer

**Target Audience:** Developers who write Python services or scripts and want a concrete checklist; no security background assumed.
**Difficulty:** Medium
**Python version:** Examples 1 and 2 were run on CPython 3.11 (python3.11 and the in-page Pyodide 0.25.1 runtime, CPython 3.11.3). Example 3 needs `sqlite3` and the `tarfile` filters, which the page runtime does not have, so it was run on python3.12 (and gave identical output on python3.13).

> **How to read this doc:** Each idea is explained

Question 8

What are dataclasses?

Accepted Answer

**Target Audience:** Python developers who write classes by hand and want to know what `@dataclass` generates, which options matter, and where its limits are.
**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). `slots`, `kw_only` and `KW_ONLY` need 3.10+.

> **How to read this doc:** Every idea is explained in plain language first, then tagged with `📌 Interview term:` so you also learn the exact

Question 9

How do you use regular expressions in Python?

Accepted Answer

**Target Audience:** Python developers who copy regexes from the internet and want to understand the `re` module well enough to write, read and debug their own
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, 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. Every output block in the **Verified**

Question 10

What is pickling and what are its risks?

Accepted Answer

**Target Audience:** Python developers who know the basics and want to understand serialisation and its security model
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (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 o

PYTHONDECODED.

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