Question 1

What are mutable and immutable types in Python?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — no prior Python knowledge assumed.
**Difficulty:** Easy
**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).

> **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 in the **Verified** section was copied from a real run o

Question 2

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 3

How does slicing with start:stop:step work?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — you only need to know what a list and a string are.
**Difficulty:** Easy
**Python version:** Checked on CPython 3.11 and the page runner (Pyodide 0.25.1 = CPython 3.11.3); the bytecode comparison was also run on CPython 3.12.

> **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 actua

Question 4

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 5

What do *args and **kwargs mean?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — you know how to write a basic `def` and call it.
**Difficulty:** Easy
**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**

Question 6

How are Python dictionaries implemented and ordered?

Accepted Answer

**Target Audience:** Beginners who use dicts daily and want to know what happens underneath; anyone preparing for a Python interview.
**Difficulty:** Easy
**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).

> **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 in the **Verified** section

Question 7

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.

##

Question 8

What is the difference between a list and a tuple?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — no prior Python knowledge assumed.
**Difficulty:** Easy
**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). Bytecode names are those of 3.11.

> **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 in the **Verified** se

Question 9

What set operations does Python support?

Accepted Answer

**Target Audience:** Beginners preparing for Python interviews — you need to know what a list is; school-level Venn diagrams help.
**Difficulty:** Easy
**Python version:** Checked on CPython 3.11 and the page runner (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:` — the precise word an interviewer expects you to use. Every output shown was produced by actually running the code on CPython 3.11 and

Question 10

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

PYTHONDECODED.

Easy

What are mutable and immutable types in Python?

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

How does slicing with start:stop:step work?

How does iterable unpacking work?

What do *args and **kwargs mean?

How are Python dictionaries implemented and ordered?

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

What is the difference between a list and a tuple?

Medium

What is the difference between shallow and deep copy?

What is structural pattern matching (match/case)?

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

How does the logging module work?

What is the @property decorator?

Why is using a mutable default argument dangerous?

What is composition versus inheritance?

What useful types does the collections module provide?

Hard

How do TypeAdapter, strict mode, and computed fields work in Pydantic v2?

What is a weak reference in Python?

How does multiprocessing share data between processes?

What is the difference between getattr and getattribute?

How does attribute lookup work on a Python object?

What is the descriptor protocol?

How do Unpack and TypedDict enable type-safe **kwargs?

What is Python 3.12's free-threaded (no-GIL) build and what changes?

PYTHONDECODED.

Easy

What are mutable and immutable types in Python?

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

How does slicing with start:stop:step work?

How does iterable unpacking work?

What do *args and **kwargs mean?

How are Python dictionaries implemented and ordered?

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

What is the difference between a list and a tuple?

Medium

What is the difference between shallow and deep copy?

What is structural pattern matching (match/case)?

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

How does the logging module work?

What is the @property decorator?

Why is using a mutable default argument dangerous?

What is composition versus inheritance?

What useful types does the collections module provide?

Hard

How do TypeAdapter, strict mode, and computed fields work in Pydantic v2?

What is a weak reference in Python?

How does multiprocessing share data between processes?

What is the difference between __getattr__ and __getattribute__?

How does attribute lookup work on a Python object?

What is the descriptor protocol?

How do Unpack and TypedDict enable type-safe **kwargs?

What is Python 3.12's free-threaded (no-GIL) build and what changes?

What is the difference between getattr and getattribute?