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 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 3

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 4

How does the in operator work in Python?

Accepted Answer

**Target Audience:** Beginners to intermediate Python developers — you should know lists, dicts and sets, and roughly what a class is.
**Difficulty:** Easy
**Python version:** Behaviour, error messages and bytecode checked on CPython 3.11; 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; all of them are repeated in

Question 5

What are Python's built-in data types?

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 6

What is the difference between an iterable and an iterator?

Accepted Answer

**Target Audience:** Python developers who loop over things every day and want the precise model behind it
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); the protocol is the same on 3.12 and 3.13

> **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 block in the **Verified** section wa

Question 7

How does a for loop work under the hood?

Accepted Answer

**Target Audience:** Python developers who write `for` loops all day and want to know exactly what the interpreter does for one
**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 also compared with CPython 3.12

> **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 block in the **V

Question 8

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

Question 9

What are generators and why use them?

Accepted Answer

**Target Audience:** Python developers who have seen `yield` and want to know what it really does and when it pays off
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, 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 block in the **Verified** section was copied from a real run of the

Question 10

What is the Method Resolution Order (MRO)?

Accepted Answer

**Target Audience:** Python developers who have used inheritance but never had to think about the order of lookup, up to candidates who need to explain C3 and `super()` precisely.
**Difficulty:** Hard
**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), with the MRO error message also checked on 3.13.

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

PYTHONDECODED.

Easy