Redis Basics

Learn the basics of Redis and how to use it with Python.

Overview

In this lesson, we will cover the basics of Redis and how to use it with Python. Redis is an in-memory key-value store that can be used for caching, real-time analytics, message queues, and more. We will cover how to install and configure Redis, and how to use it with Python.

Lesson Content

In this lesson, we will cover:

• Redis basics
• Installing and configuring Redis
• Using Redis with Python

Redis Basics

Redis is an in-memory key-value store that can be used for caching, real-time analytics, message queues, and more. Redis stores data in memory, which makes it very fast, but also means that it is limited by the amount of available memory.

Redis data is organized into key-value pairs, where the key is a string and the value can be any Redis data type, such as a string, hash, list, set, or sorted set. Redis provides a rich set of commands for working with data, including commands for manipulating strings, hashes, lists, sets, and sorted sets, as well as more advanced commands for working with data structures such as bitmaps and hyperloglogs.

Installing and Configuring Redis

Pick whichever option suits your computer:

Raspberry Pi OS, Debian or Ubuntu

sudo apt update
sudo apt install redis-server

The server starts automatically and runs in the background.

macOS (with Homebrew)

brew install redis
brew services start redis

Any computer with Docker (including Windows)

docker run -d --name redis -p 6379:6379 redis

See the Docker course if you’re new to Docker.

To check Redis is running, use the redis-cli command-line tool (inside Docker, use docker exec -it redis redis-cli):

redis-cli ping

If you see PONG, you’re ready. You can type any Redis command into redis-cli to try it out, which is handy for the command examples in later lessons.

By default, Redis listens on port 6379, but you can change this in the Redis configuration file.

Install the Python library

pip install redis

On Raspberry Pi OS, create and activate a virtual environment first (python3 -m venv ~/redis-env then source ~/redis-env/bin/activate).

Using Redis with Python

To use Redis with Python, you can use the Redis Python library, which provides a Pythonic interface to Redis. Here’s an example of how to use Redis with Python:

import redis

redis_client = redis.Redis(host='localhost', port=6379, decode_responses=True)

# Set a string value
redis_client.set('mykey', 'myvalue')

# Get a string value
value = redis_client.get('mykey')
print(value)   # myvalue

# Delete a key
redis_client.delete('mykey')

In this example, we create a Redis client with redis.Redis(), which connects to the Redis server on localhost at port 6379. We then use set() to store a string value for the key mykey, and get() to retrieve it. Finally, delete() removes the key and its value.

Bytes or strings?

Redis stores everything as bytes. Without decode_responses=True, get() returns b'myvalue' instead of 'myvalue'. We use decode_responses=True throughout this course so you get normal Python strings back.

Keys that expire

One of Redis’s handiest tricks is that keys can delete themselves after a set time. That’s perfect for caching:

redis_client.set('weather', 'sunny', ex=60)   # expires in 60 seconds
print(redis_client.ttl('weather'))            # seconds left to live

Key Takeaways

After completing this lesson, you should be able to:

• Describe the basics of Redis and its data model
• Install and configure Redis
• Use Redis with Python

Conclusion

In this lesson, we covered the basics of Redis and how to use it with Python. We described Redis and its data model, and demonstrated how to install and configure Redis, and how to use Redis with Python using the Redis Python library. In the next lesson, we will cover Redis data types.

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