Redis HSTRLEN in Python (Detailed Guide w/ Code Examples)

Use Case(s)

The Redis HSTRLEN command is used to get the length of the value of a hash field stored at key. It returns the string length of the value associated with field in the hash stored at key. In Python, using the redis-py client, we can use this command as hstrlen(name, key).

Common use cases include:

  • Validating text data length before processing it further.
  • Implementing application side checks for length constraints.

Code Examples

Let's consider that we have a hash representing a user object stored in Redis with 'user_id' as the key and a dictionary as the value.

import redis r = redis.Redis(host='localhost', port=6379, db=0) # Assume we have the following hash in redis user_dict = {"name": "John Doe", "email": ""} r.hmset("user:1001", user_dict) # Now let's check the length of the email field email_length = r.hstrlen("user:1001", "email") print(email_length) # Output: 18

In this example, first we connected to our local Redis server. We then created a hash with the key 'user:1001' and a dictionary with "name" and "email" fields as the value. Afterwards, we used hstrlen command to get the length of the email field in our hash.

Best Practices

  • Always check if the key and field exist before running an hstrlen command to avoid errors.
  • If you know that some fields may contain large strings, try to use hstrlen instead of hget to reduce memory usage when you only need the length of a field.

Common Mistakes

  • One common mistake is forgetting that hstrlen will return 0 if the key or the field does not exist.
  • Another one is using hget and then calculating string length in Python when you only need the string length. This can consume a lot of memory for large strings. Instead, use hstrlen.


  1. What happens if the key or field does not exist?

    • The hstrlen command will return 0 if the key or the field does not exist.
  2. Can I use hstrlen for any data type in Redis?

    • No, hstrlen is specifically designed for hash fields. For other data types, you might need different commands.

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