LPOS - Upstash Documentation

Use LPOS to find the position of an element in a list.

The scan starts at the head and, by default, reports the index of the first match or null when there is none. RANK selects which match to report: RANK 2 skips to the second occurrence, and a negative rank searches backwards from the tail, so RANK -1 finds the last occurrence. COUNT returns that many matching indexes instead of just one, and COUNT 0 returns all of them. MAXLEN limits how many elements are compared, which bounds the cost of the search on a long list at the price of possibly missing matches beyond that point.

It is the read-only way to locate a value before acting on it with LSET or LREM.

Syntax#

LPOS <key> <element> [RANK <rank>] [COUNT <num-matches>] [MAXLEN <len>]

Arguments#

Argument	Required	Repeatable	Description
`<key>`	Yes	No	Redis key targeted by the command.
`<element>`	Yes	No	Element value to search for.
`RANK <rank>`	No	No	Which match to return; negative values search from the tail.
`COUNT <num-matches>`	No	No	Number of matches to return; `0` returns every match.
`MAXLEN <len>`	No	No	Maximum number of entries to keep in the stream.

Response#

The reply reports the result of the operation. Error replies have the same shape in RESP2 and RESP3 and are surfaced as exceptions by the SDKs below.

Protocol	Reply
RESP2	Null bulk string or null array, Integer, or array of integer positions
RESP3	Null, Integer, or array of integer positions

Note

Client libraries often decode bulk strings, maps, sets, and numeric strings into language-native values. The table describes the Redis wire reply.

Examples#

TCP examples use the TLS REDIS_URL from the Upstash console. REST examples use UPSTASH_REDIS_REST_URL and UPSTASH_REDIS_REST_TOKEN.

Redis CLI

LPOS my-key element

@upstash/redis

import { Redis } from "@upstash/redis";const redis = Redis.fromEnv();await redis.rpush("key", "a", "b", "c");const index = await redis.lpos("key", "b");console.log(index); // 1

upstash_redis

from upstash_redis import Redisredis = Redis.from_env()result = redis.lpos("my-key", "element")print(result)

ioredis

import Redis from "ioredis";const redis = new Redis(process.env.REDIS_URL!);const result = await redis.lpos("my-key", "element");console.log(result);

node-redis

import { createClient } from "redis";const client = await createClient({ url: process.env.REDIS_URL })  .on("error", console.error)  .connect();const result = await client.lPos("my-key", "element");console.log(result);

redis-py

import osimport redisclient = redis.from_url(os.environ["REDIS_URL"])result = client.lpos("my-key", "element")print(result)

go-redis

package mainimport (    "context"    "fmt"    "os"    "github.com/redis/go-redis/v9")func main() {    opts, err := redis.ParseURL(os.Getenv("REDIS_URL"))    if err != nil {        panic(err)    }    client := redis.NewClient(opts)    result, err := client.LPos(context.Background(), "my-key", "element", redis.LPosArgs{}).Result()    if err != nil {        panic(err)    }    fmt.Println(result)}

jedis

import java.net.URI;import redis.clients.jedis.Jedis;try (Jedis jedis = new Jedis(new URI(System.getenv("REDIS_URL")))) {  Object result = jedis.lpos("my-key", "element");  System.out.println(result);}

redis-rs

use redis::{LposOptions, TypedCommands};fn main() -> redis::RedisResult<()> {    let url = std::env::var("REDIS_URL").expect("REDIS_URL is not set");    let client = redis::Client::open(url)?;    let mut connection = client.get_connection()?;    let result: Option<isize> = connection.lpos("my-key", "element", LposOptions::default())?;    println!("{result:?}");    Ok(())}