Day 4: Dictionaries Are Magic (Until They Aren’t) — Hashing & Collisions

Sun, 26 Apr 2026 00:00:00 +0000

You think dictionary lookup is always O(1). That’s only half the story.

Today, you understand how dictionaries actually work.

Today’s Goal

By the end of today, you will:

user = {
 "name": "John",
 "age": 30
}

You think:

This is just key-value storage

Reality:

This is a highly optimized hash table

key -> hash(key) -> index -> slot -> value

Dictionary does NOT scan all keys. It jumps directly using hash.