Question 1

What is the Global Interpreter Lock (GIL)?

Accepted Answer

**Target Audience:** Python developers who have used or heard of threads and want to understand what CPython actually allows. No operating-systems background is assumed.
**Difficulty:** Medium
**Python version:** Behaviour checked on standard (GIL) builds of CPython 3.11, 3.12 and 3.13. Example 1 also runs in the page on Pyodide 0.25.1 (CPython 3.11.3); Example 2 uses real threads, which the browser build cannot start, so it is verified on 3.12.

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

Question 2

When do you use threading, multiprocessing, or asyncio?

Accepted Answer

**Target Audience:** Developers who know the words thread, process and async but want a reliable way to pick one — no prior concurrency experience needed.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (standard GIL builds); the in-page example runs on Pyodide 0.25.1 (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 expect

Question 3

What is asyncio.TaskGroup and why does it replace gather?

Accepted Answer

**Target Audience:** Developers who have written `asyncio` code with `gather` or `create_task` and want to know what TaskGroup changes and when to pick which.
**Difficulty:** Medium
**Python version:** `TaskGroup` needs Python 3.11+. Behaviour checked on CPython 3.11, 3.12 and 3.13 (same output); both examples also run in this page on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Every idea comes in plain language first. Words an interviewer expects you to use are tagged `📌 Inte

Question 4

How do ThreadPoolExecutor and ProcessPoolExecutor work?

Accepted Answer

**Target Audience:** Developers who have used a loop and a function, and want to run that function many times at once safely — no prior concurrency knowledge needed.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (standard GIL builds); the in-page example runs on Pyodide 0.25.1 (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 intervi

Question 5

What is the difference between concurrency and parallelism in Python?

Accepted Answer

**Target Audience:** Python developers who have heard of threads and asyncio but mix up the two words — no prior concurrency knowledge needed.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (standard GIL builds); the in-page example runs on Pyodide 0.25.1 (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 out

Question 6

How does async/await work in Python?

Accepted Answer

**Target Audience:** Python developers who have seen `async`/`await` in FastAPI, aiohttp or asyncio examples and want to understand what it really does, from the coroutine object up to the event loop.
**Difficulty:** Hard
**Python version:** Example 1 uses no asyncio at all and runs in the page on Pyodide 0.25.1 (CPython 3.11.3); it was checked on CPython 3.11 and 3.12. Example 2 uses `asyncio.run()`, which the in-page runner cannot call (the page itself already runs inside an event loop), so it

PYTHONDECODED.

Medium