Hi team, I was having some trouble with

map_task

and solved it so I thought I’d share the solution in case anyone else does too. I was using tasked wrapped in

partial

and the curried argument was a

FlyteFile

. Getting an error like

TypeError: object of type 'FlyteFile' has no len()

Here’s an simplified example (task bodies omitted for brevity

@task()
def download_files() -> list[FlyteFile]:
    ...
    return file_list


@task()
def get_checkpoint() -> FlyteFile:
    ...
    return checkpoint_file


@task()
def process_file(file: FlyteFile, model: FlyteFile) -> dict:
    ...
    return result


@workflow
def process_all_files() -> list[dict]:
    file_list = download_files()
    model = get_checkpoint()

    process_using_model = partial(
        process_file,
        model=model,
    )
    result = map_task(process_using_model)(file=file_list)

    return result

The error was in the task definition,

def process_file(model: FlyteFile, file: FlyteFile)

should have been

process_file(file: FlyteFile, model: FlyteFile)

. Notice how the arguments for the map task are defined after the argument which is supplied from the list. This was a tough one to work out and I think should either be changed to make it more generic, or mentioned in the docs.

Ohh are you saying this is an ordering or arguments problem

Thanks for reporting this @Joe Hartshorn, this seems like a bug… can you open up an issue? [flyte-bug]

🐞 Create a new Flyte Bug issue: https://github.com/flyteorg/flyte/issues/new?assignees=&labels=bug%2Cuntriaged&template=bug_report.yaml&title=%5BBUG%5D+

@Yee @Eduardo Apolinario (eapolinario)

Happy to open a bug! It’s not local, only remote, and it’s definitely an ordering issue. Edit: I have a minimal reproducible example I can post in a bug.