Q: How does comparison chaining (a < b < c) work?

**Target Audience:** Beginners who have seen `0 **How to read this doc:** Plain words first, then a `📌 Interview term:` callout with the exact term. All outputs are from real runs; the **Verified** section quotes them in full. ## 1. Why This Eve

Question 1

How do you work with dictionaries (get, setdefault, items, merging)?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — no prior knowledge assumed beyond variables and lists.
**Difficulty:** Easy
**Python version:** Checked on CPython 3.11 and the page runner (Pyodide 0.25.1 = CPython 3.11.3). The `|` and `|=` operators need Python 3.9 or newer.

> **How to read this doc:** Each idea is explained in plain language first, then tagged with `📌 Interview term:` — the precise word an interviewer expects you to use. Every output shown was produced by act

Question 2

How does iterable unpacking work?

Accepted Answer

**Target Audience:** Beginners to intermediate Python developers — you should know what a list and a tuple are.
**Difficulty:** Easy
**Python version:** Behaviour and `dis` output checked on CPython 3.11 (3.12 where noted); the 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. Words an interviewer expects you to use are tagged `📌 Interview term:` and defined on the spot, then listed again in the Quick Glossary. All

Question 3

What are f-strings?

Accepted Answer

**Target Audience:** Beginners formatting their first output; candidates who want the format mini-language, the CPython detail and the version history.
**Difficulty:** Easy
**Python version:** f-strings exist since Python 3.6. Examples 1 and 2 checked on CPython 3.11.17 and in the page runner (Pyodide 0.25.1, CPython 3.11.3); Example 3 needs 3.12+ and was checked on 3.12.3 and 3.13.16.

> **How to read this doc:** Every idea is explained in plain words first, then tagged `📌 Interview term:` wit

Question 4

What is the difference between __repr__ and __str__?

Accepted Answer

**Target Audience:** Beginners who have written a class or two, up to intermediate developers revising for interviews.
**Difficulty:** Easy
**Python version:** Behaviour checked on CPython 3.11 and 3.13 (identical output); every example also runs 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. When a word appears that an interviewer expects you to know, it is tagged with `📌 Interview term:` and defined right there. All

Question 5

How does comparison chaining (a < b < c) work?

Accepted Answer

**Target Audience:** Beginners who have seen `0 <= x < 10` and want to know exactly what it means; candidates who want the CPython detail.
**Difficulty:** Easy
**Python version:** Checked on CPython 3.11.17 and in the page runner (Pyodide 0.25.1, CPython 3.11.3); bytecode also shown from 3.13.16.

> **How to read this doc:** Plain words first, then a `📌 Interview term:` callout with the exact term. All outputs are from real runs; the **Verified** section quotes them in full.

## 1. Why This Eve

Question 6

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 7

Why is using a mutable default argument dangerous?

Accepted Answer

**Target Audience:** Beginners to intermediate — you can write functions with default values.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11.17 and in the page runner (Pyodide 0.25.1, CPython 3.11.3); the dataclass error message was also checked on 3.12.3.

> **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 actual

Question 8

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 9

How does a + b dispatch in Python?

Accepted Answer

**Target Audience:** Beginners to intermediate Python developers who have written a class and want to know how operators work on it.
**Difficulty:** Medium
**Python version:** Behaviour and bytecode checked on CPython 3.11 (outputs identical on 3.12 and 3.13); both examples also run in the page on Pyodide 0.25.1 (CPython 3.11.3).

> **How to read this doc:** Plain language first; terms an interviewer expects are tagged `📌 Interview term:` and defined where they appear, then repeated in the Quic

Question 10

What is the difference between the call stack and the heap in Python?

Accepted Answer

**Target Audience:** Developers coming from C, C++, Java or Go who want to map "stack vs heap" onto Python, and Python developers debugging recursion or memory
**Difficulty:** Medium
**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); all gave identical output

> **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

PYTHONDECODED.

Easy

How do you work with dictionaries (get, setdefault, items, merging)?

How does iterable unpacking work?

What are f-strings?

What is the difference between repr and str?

How does comparison chaining (a < b < c) work?

What is the walrus operator?

Medium

Why is using a mutable default argument dangerous?

What are common Python security pitfalls?

How does a + b dispatch in Python?

What is the difference between the call stack and the heap in Python?

How do default, keyword-only and positional-only parameters work?

What are generators and why use them?

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

What is Python 3.12's new type parameter syntax (type, generic classes)?

Hard

How does the Python import system work?

How does CPython execute your code?