Getting Default TTL in Redis Using Python (Detailed Guide w/ Code Examples)
Use Case(s)
In Redis, TTL (Time To Live) is used to set an expiry time on keys. You might want to get the default TTL of a key if you are managing session cookies or caching data and need to know the preset expiration timeline.
Code Examples
Example 1: Getting TTL of a Key
Here's how you can get the TTL of a key using python's redis
library:
import redis r = redis.Redis(host='localhost', port=6379, db=0) r.set('my_key', 'my_value', ex=10) ttl = r.ttl('my_key') print(ttl) # outputs: 10
In this example, we first connect to the Redis server. Then, we set a key my_key
with value my_value
and an expiration time of 10 seconds. r.ttl('my_key')
is used to get the TTL of my_key
. The print statement will output 10.
Example 2: Handling Non-Existent Keys or Keys Without TTL
When a key does not exist or doesn't have a TTL, the ttl
function will return None.
import redis r = redis.Redis(host='localhost', port=6379, db=0) ttl = r.ttl('non_existent_key') print(ttl) # outputs: None
In this example, since there's no key named 'non_existent_key', the ttl
function will return None.
Best Practices
- Be sure to handle the case where the TTL can return None - when a key does not exist or doesn't have an expiration time set.
- Avoid setting a very short TTL for keys that are frequently accessed and rarely changed, as it could lead to unnecessary overhead of setting the same key-value pair repeatedly.
Common Mistakes
- Using
ttl
on a key without checking if it exists or not can lead to Null Pointer Exceptions. - Misunderstanding that
ttl
returns time in seconds. Remember, it can return-1
if the key exists but has no associated expire.
FAQs
Q: What happens if I use ttl
on a key that never expires?
A: If the key exists but does not have an expiration set, ttl
will return -1
.
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