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

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 3

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

PYTHONDECODED.

Medium

What is the Global Interpreter Lock (GIL)?

How do ThreadPoolExecutor and ProcessPoolExecutor work?

What is the difference between concurrency and parallelism in Python?