Question 1

What is the difference between '==' and 'is'?

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); the warning text was also checked on 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 shown in the **Veri

Question 2

How do you sort with a custom key, and how does sorted differ from sort?

Accepted Answer

**Target Audience:** Beginners to intermediate Python developers — you should know lists, tuples and simple functions.
**Difficulty:** Easy
**Python version:** Behaviour 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:** Each idea comes in plain language first. Words an interviewer expects you to know are tagged `📌 Interview term:` and defined on the spot; the Quick Glossary at the end lists them all. Every output and comp

Question 3

How do you convert between Python objects and JSON?

Accepted Answer

**Target Audience:** Beginners learning Python, and developers who want the edge cases an interviewer probes
**Difficulty:** Easy
**Python version:** Behaviour checked on CPython 3.11 (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 4

What is the difference between shallow and deep copy?

Accepted Answer

**Target Audience:** Beginners who have been surprised by "I changed the copy and the original changed too", and anyone preparing for the classic interview follow-ups on `copy`.
**Difficulty:** Medium
**Python version:** Behaviour checked on CPython 3.11 and 3.13, and in the page runner (Pyodide 0.25.1, CPython 3.11.3). `copy.replace()` needs 3.13.

> **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

Question 5

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 6

How do you create and chain custom exceptions?

Accepted Answer

**Target Audience:** Python developers who know try/except and want to design errors for a library or service
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); `add_note` needs 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 block in the **Verified** section was copied from a

Question 7

How do you handle dates, times and time zones in Python?

Accepted Answer

**Target Audience:** Python developers who store, compare or display timestamps and want to get time zones and daylight saving time right
**Difficulty:** Medium
**Python version:** Checked on CPython 3.11 (Example 1, also in this page on Pyodide 0.25.1) and CPython 3.12 (Example 2, which needs the IANA time zone database)

> **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. Ever

Question 8

How does the Python import system work?

Accepted Answer

**Target Audience:** Python developers who know how to import things and want to know how importing works, and candidates for senior Python interviews
**Difficulty:** Hard
**Python version:** Every example was run on CPython 3.11 (and in this page on Pyodide 0.25.1, which is CPython 3.11.3); Example 2 also gave identical output on 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

PYTHONDECODED.

Easy