Lists & Hashes: Overview

🎁 Run Redis in Docker first

Start a local Redis, then open its CLI:

docker run -d --name redis -p 6379:6379 redis:7-alpine
docker exec -it redis redis-cli

Leave this CLI open and paste each lesson's commands into it. (No Docker? Install Redis locally.)

Two powerful types in one module

This module introduces two of Redis’s most useful data structures: Lists and Hashes.

A List is an ordered collection of strings backed by a doubly-linked list. You can push and pop elements from either end in O(1) time — no matter how many items are in the list. That makes lists ideal for queues, stacks, activity feeds, and recent-item trackers.

A Hash is a field-value map stored under a single key — think of it as a Python dict or a JavaScript object. You can set and get individual fields atomically, which means you can update a user’s email without touching any of their other attributes.

127.0.0.1:6379> RPUSH notifications "login" "purchase" "logout"
(integer) 3
127.0.0.1:6379> LRANGE notifications 0 -1
1) "login"
2) "purchase"
3) "logout"
127.0.0.1:6379> HSET user:1 name "Ada" email "[email protected]" age "30"
(integer) 3
127.0.0.1:6379> HGETALL user:1
1) "name"
2) "Ada"
3) "email"
4) "[email protected]"
5) "age"
6) "30"

When to use each type

Type	Use when you need…	Examples
List	Ordered elements, O(1) head/tail access	Message queues, activity feeds, recent searches
Hash	Named fields on one key, partial updates	User profiles, product records, session data

What this module covers

Lesson	Topic
Lists & Hashes: Overview	This page — Lists, Hashes, when to use each
Lists	LPUSH, RPUSH, LRANGE, LLEN, LINDEX, LSET, LREM, LTRIM
Lists as Queues & Stacks	LPUSH+RPOP (FIFO), LPUSH+LPOP (stack), BLPOP/BRPOP
Hashes	HSET, HGET, HMGET, HGETALL, HDEL, HEXISTS, HKEYS, HVALS, HLEN
Hash Objects	Modeling objects, HINCRBY, HINCRBYFLOAT, HSETNX

A quick taste of both types

Try pushing items onto a list and storing fields in a hash:

127.0.0.1:6379> RPUSH tasks "write tests" "deploy" "notify team"
(integer) 3
127.0.0.1:6379> LRANGE tasks 0 -1
1) "write tests"
2) "deploy"
3) "notify team"
127.0.0.1:6379> HSET product:99 name "Widget" price "9.99" stock "100"
(integer) 3
127.0.0.1:6379> HGET product:99 name
"Widget"
127.0.0.1:6379> HGET product:99 price
"9.99"

RPUSH tasks "write tests" "deploy" "notify team"
LRANGE tasks 0 -1
HSET product:99 name "Widget" price "9.99" stock "100"
HGET product:99 name
HGET product:99 price