Question 1

What are list/dict/set comprehensions?

Accepted Answer

**Target Audience:** Beginners to intermediate Python developers — you should be comfortable with `for` loops and lists.
**Difficulty:** Easy
**Python version:** Behaviour checked on CPython 3.11, with the scope and bytecode differences also run on 3.12 and 3.13; the examples run in the page on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Every idea is explained in plain language first, then the precise word an interviewer expects is tagged `📌 Interview term:` and defined. The

Question 2

What is the walrus operator?

Accepted Answer

**Target Audience:** Beginners who have seen `:=` and want to know when it helps; candidates who want the scope and syntax rules.
**Difficulty:** Easy
**Python version:** Available since Python 3.8. Behaviour checked on CPython 3.11.17 (and 3.13.16, same output) and in the page runner (Pyodide 0.25.1, CPython 3.11.3).

> **How to read this doc:** Every idea is explained in plain words, then tagged `📌 Interview term:` with the name an interviewer expects. All output is from real runs, collected

Question 3

What is the LEGB rule for scope resolution?

Accepted Answer

**Target Audience:** Python beginners and intermediate developers preparing for interviews — you only need to know what a function is.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13; the examples run in the page 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 output shown was produced by

Question 4

What are lambda functions and map/filter/reduce?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — you know lists, loops and basic functions.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11.17 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 actually running the code; the **Verified** sect

Question 5

What is the memory difference between a list comprehension and a generator expression?

Accepted Answer

**Target Audience:** Python developers who know both syntaxes and want to be able to quantify and explain the difference
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); bytecode compared with CPython 3.12. Byte counts are from 64-bit CPython; Pyodide is a 32-bit build, so the examples print comparisons, not raw numbers

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

Question 6

What is the late-binding closure pitfall in loops?

Accepted Answer

**Target Audience:** Python beginners and intermediate developers preparing for interviews — you should know what a lambda and a list comprehension are.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13; the examples run in the page 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 output show

Question 7

How does a Python list grow in memory?

Accepted Answer

**Target Audience:** Developers who use lists every day and want the memory model an interviewer asks about; no C knowledge needed.
**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 growth rule is a CPython implementation detail and has changed between versions.

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

Question 8

What is an async iterator and async for?

Accepted Answer

**Target Audience:** Python developers who know normal `for` loops, iterators and the basics of `async def` / `await`, and want the exact protocol an interviewer probes.
**Difficulty:** Hard
**Python version:** Behaviour checked on CPython 3.11, 3.12 and 3.13 (same output on all three); 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 `📌 Interview term

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