Retrieving Multiple Values from Redis in Python (Detailed Guide w/ Code Examples)

Use Case(s)

In Python, retrieving multiple values from Redis is a common operation when you have to process or analyze a group of related data elements at once. This can be particularly useful in applications that need to fetch user profiles, configuration settings, session information, or other groups of related data.

Code Examples

Example 1: Retrieve multiple keys using mget()

Here's how to use the mget() function in Redis-py:

import redis
r = redis.Redis(host='localhost', port=6379, db=0)

keys = ['key1', 'key2', 'key3']
values = r.mget(keys)
print(values)

In this code, we first establish a connection with the Redis server. Then we define a list of keys for which we want to retrieve the values. The mget() function retrieves the values associated with each key in the list.

Example 2: Handle non-existent keys with mget()

It's important to note that mget() will return None for any key that does not exist:

non_existent_keys = ['key4', 'key5']
values = r.mget(non_existent_keys)
print(values)  # Outputs: [None, None]

Here, 'key4' and 'key5' do not exist in the Redis database, so mget() returns None for these keys.

Best Practices

• Always check for None in the result list after calling mget(), as it signifies that the corresponding key did not exist in the Redis database.
• Use mget() instead of multiple get() calls to reduce network latency and improve application performance.

Common Mistakes

• Not handling None values returned by mget() can lead to unexpected behavior or errors.

FAQs

Q: What does mget() return if a key doesn't exist in the database?

A: mget() will return None for any key that does not exist in the Redis database.