Dictionaries

Security notes, SOC lab write-ups and tested code by Mahir Faysal, a SOC Level 1 cybersecurity learner in Bangladesh, plus notes from my Next.js and Gemini projects. Sample posts are marked and drafts stay in the admin area.

All notes Coding tips · 166 Learning notes · 25 Practice · 1

Coding tips

KeyError: 'x' in Python: 10 Causes and Fixes (dict, .get, JSON, pandas tips)

Python raises KeyError when you look up a missing key with square brackets. Here are 10 real causes, from a typo and nested JSON to pandas column labels, with the exact tracebacks from my tests and the fixes that stop the crash.

November 6, 2026 · 11 min read · 7 views