Flask-Redis Integration

0.4.0 · maintenance · verified Thu Apr 16

Flask-Redis is a Flask extension that provides a convenient way to integrate Redis into your Flask applications. It abstracts away the direct management of Redis connections, allowing you to easily access a Redis client instance configured through your Flask app's configuration. The current version is 0.4.0, with the last release in 2019, indicating a maintenance-only or stable state.

Common errors

```
TypeError: init_app() got an unexpected keyword argument 'strict'
```
cause Attempting to pass the `strict` parameter to `init_app()` with flask-redis versions 0.3.0 or later.

fix The `strict` parameter should be passed during the `FlaskRedis` instance creation: `redis_client = FlaskRedis(strict=True)` (if not passing `app` initially) or `redis_client = FlaskRedis(app, strict=True)`.
```
KeyError: 'redis'
```
cause Trying to access the Redis client via `app.extensions['redis']` when the extension has not been initialized or the key is incorrect. This can happen if the config prefix was changed, or if running a version older than 0.3.0 (where the key might have been 'REDIS').

fix Ensure `FlaskRedis(app)` or `FlaskRedis().init_app(app)` has been called. If using default config, access via `app.extensions['redis']`. If you changed the config prefix, remember it's lowercased: `app.extensions[your_prefix.lower()]`.
```
DeprecationWarning: flask_redis.Redis is deprecated, use flask_redis.FlaskRedis instead
```
cause Using the old class name `Redis` from `flask_redis` module which was renamed.

fix Change your import statement from `from flask_redis import Redis` to `from flask_redis import FlaskRedis` and update all instances of `Redis(...)` to `FlaskRedis(...)`.

Warnings

breaking The `FlaskRedis.init_app` method no longer accepts a `strict` parameter.
Fix: Pass the `strict` flag directly when instantiating `FlaskRedis`: `redis_client = FlaskRedis(app, strict=True)` instead of `redis_client.init_app(app, strict=True)`.
breaking The extension is now registered under the lowercase version of its config prefix (default: 'redis') in `app.extensions`.
Fix: Access the extension using `app.extensions['redis']` (if using default prefix) or `app.extensions[app.config['REDIS_CONFIG_PREFIX'].lower()]`.
deprecated The class `flask_redis.Redis` was renamed to `flask_redis.FlaskRedis`.
Fix: Update your import statement from `from flask_redis import Redis` to `from flask_redis import FlaskRedis` and update class instantiations.
deprecated Setting `REDIS_DATABASE` (or equivalent) in config is deprecated in favor of including the database number in `REDIS_URL`.
Fix: Use the `REDIS_URL` configuration key (e.g., `redis://localhost:6379/0` for database 0) and remove separate `REDIS_DATABASE` settings.

Install

pip install flask-redis Install latest version

Imports

FlaskRedis
```
from flask_redis import FlaskRedis
```
Redis
wrong:
```
from flask_redis import Redis
```
correct:
```
from flask_redis import FlaskRedis
```
The class was renamed from `Redis` to `FlaskRedis` in v0.1.0. Using the old name emits a `DeprecationWarning` and will be removed in future versions.

Quickstart

This quickstart demonstrates how to initialize Flask-Redis with your Flask application and use the Redis client. It sets the Redis URL via application configuration, which can be overridden by an environment variable. The Redis client instance is then directly available for use, typically within request contexts or blueprints.

import os
from flask import Flask
from flask_redis import FlaskRedis

app = Flask(__name__)

# Configure Redis URL from environment variable or default
app.config['REDIS_URL'] = os.environ.get('REDIS_URL', 'redis://localhost:6379/0')

# Initialize Flask-Redis with the app
redis_client = FlaskRedis(app)

@app.route('/')
def index():
    try:
        redis_client.set('mykey', 'hello from flask-redis!')
        value = redis_client.get('mykey')
        if value:
            return f"Value from Redis: {value.decode()}"
        return "No value found in Redis."
    except Exception as e:
        return f"Error connecting to Redis: {e}"

if __name__ == '__main__':
    # Make sure a Redis server is running or set REDIS_URL environment variable
    print(f"Redis URL: {app.config['REDIS_URL']}")
    app.run(debug=True)

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