redis/redis-py · error · TypeError

Async Redis client does not support class retrieval

Error message

Async Redis client does not support class retrieval

What it means

Raised by AsyncBasicKeyCommands.__getitem__ (a TypeError) when you use 'async_client[key]' to read a value. The sync client maps client[key] to GET (raising KeyError on missing), but the async dunder cannot be awaited, so it is disabled to prevent receiving a coroutine instead of the value.

Solutions

Replace "client[key]" with "await client.get(key)".
If you relied on KeyError for missing keys, check for None or use a helper that raises KeyError when get returns None.

Example fix

# before
value = client['mykey']

# after
value = await client.get('mykey')

Defensive patterns

Strategy: validation

Validate before calling

# Never use client[key] on an async client; call get explicitly.
value = await client.get(key)  # instead of client[key]

Type guard

import redis

def is_async_client(c) -> bool:
    return isinstance(c, (redis.asyncio.Redis, redis.asyncio.RedisCluster))

Try / catch

try:
    value = client[key]
except TypeError as e:
    if 'class retrieval' in str(e):
        value = await client.get(key)
    else:
        raise

Prevention

Replace client[key] with await client.get(key) in all async code paths.
If you relied on KeyError for missing keys, check value is None and raise KeyError yourself.

When it happens

Trigger: Writing "value = client['mykey']" where client is a redis.asyncio.Redis instance.

Common situations: Direct port of sync code that used dict-style key access. Generic code that treats the client as a mapping.

Related errors

AI-assisted analysis of redis/redis-py@6a6b581b48 (2026-08-10). Data as JSON: /api/errors/57e42b9255047bc2. Report an issue: GitHub.

Appendix: source

Thrown at redis/commands/core.py:4815

            pieces.append("LEN")
        if idx:
            pieces.append("IDX")
        if minmatchlen is not None and minmatchlen != 0:
            pieces.extend(["MINMATCHLEN", minmatchlen])
        if withmatchlen:
            pieces.append("WITHMATCHLEN")
        return self.execute_command("LCS", *pieces, keys=[key1, key2])


class AsyncBasicKeyCommands(BasicKeyCommands):
    def __delitem__(self, name: KeyT):
        raise TypeError("Async Redis client does not support class deletion")

    def __contains__(self, name: KeyT):
        raise TypeError("Async Redis client does not support class inclusion")

    def __getitem__(self, name: KeyT):
        raise TypeError("Async Redis client does not support class retrieval")

    def __setitem__(self, name: KeyT, value: EncodableT):
        raise TypeError("Async Redis client does not support class assignment")

    async def watch(self, *names: KeyT) -> None:
        return super().watch(*names)

    async def unwatch(self) -> None:
        return super().unwatch()


class ListCommands(CommandsProtocol):
    """
    Redis commands for List data type.
    see: https://redis.io/topics/data-types#lists
    """

    @overload

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