@ancient-wolf-19325 When I want to return multiple promise values from tasks I start in a sub-workflow, what are the possible syntaxes to return these?

You can return multiple promise values from tasks in a sub-workflow by returning a tuple, a NamedTuple, or a dataclass from the sub-workflow. The most common syntaxes are: 1. Tuple: Return a tuple of promises, e.g.,

return t1(), t2()

. 2. NamedTuple: Define a NamedTuple type and return it, e.g.,

return MyOutputs(a=t1(), b=t2())

. 3. Dataclass: Use a dataclass (with JSON serialization support) and return an instance, e.g.,

return MyDataClass(a=t1(), b=t2())

. All these approaches are supported and strongly typed in Flyte workflows and subworkflows, as described in the Flyte user guide and demonstrated in Flyte's type hints tests. Would you like more detail or code examples for each syntax? Sources: - Flyte user guide - Flyte's type hints tests 👍 0 button 👎 0 button 💡 Hint: Mention @runllm in the thread for followups.

@ancient-wolf-19325 Let's say I promises valueX, valueY and valueZ that get their values from taskX, taskY and taskZ and I want to return these as a json. What is the correct way to return these?

The correct way to return multiple promise values as a JSON object in Flyte is to define a dataclass with the desired fields (e.g.,

valueX

,

valueY

,

valueZ

), ensure it supports JSON serialization (e.g., using

mashumaro.mixins.json.DataClassJSONMixin

or

dataclasses_json

for older Flytekit versions), and return an instance of this dataclass from your workflow or subworkflow. Flyte will serialize the dataclass as a single complex JSON object. See the Flyte dataclass documentation and user guide for examples. Would you like a step-by-step code example? Sources: - Flyte user guide: dataclass - Flyte dataclass documentation 👍 0 button 👎 0 button 💡 Hint: Mention @runllm in the thread for followups.

@ancient-wolf-19325 Give an example on creating a dataclass and returning it as json

Define a Python dataclass with typed fields, return it from a Flyte task, and Flyte will serialize it as JSON. For Flytekit ≥1.14, use the standard

@dataclass

decorator; for older versions, add

@dataclass_json

or inherit from

DataClassJSONMixin

. Example:

from dataclasses import dataclass
import flytekit
from flytekit import task, workflow

@dataclass
class MyResult:
    valueX: int
    valueY: str
    valueZ: float

@task
def make_result(x: int, y: str, z: float) -> MyResult:
    return MyResult(valueX=x, valueY=y, valueZ=z)

@workflow
def wf(x: int, y: str, z: float) -> MyResult:
    return make_result(x=x, y=y, z=z)

This will return a JSON object with fields

valueX

,

valueY

, and

valueZ

. See Flyte dataclass docs for more. Would you like more detail or an example with custom serialization? Sources: - Flyte user guide: dataclass 👍 0 button 👎 0 button 💡 Hint: Mention @runllm in the thread for followups.

@ancient-wolf-19325 Do i need to package the return in a task or can i do it without the task, straight from workflow?

You cannot directly instantiate and return a dataclass (or any value) from a workflow body; you must package the return in a task. Workflow bodies in Flyte are a Python-like DSL that only allow chaining tasks and passing promises, not executing arbitrary Python code or constructing objects directly (Flyte workflows vs tasks, Flyte user guide). Would you like more detail on why this restriction exists or how to structure your code? Sources: - Flyte workflows vs tasks 👍 0 button 👎 0 button 💡 Hint: Mention @runllm in the thread for followups.

@ancient-wolf-19325 Can I have in one dataclass another dataclass, if so what is the syntax. Give example

Yes, you can nest one dataclass inside another in Flyte. The syntax is to define both dataclasses and use the inner dataclass as a typed field in the outer dataclass. Example:

from dataclasses import dataclass

@dataclass
class Inner:
    a: int
    b: str

@dataclass
class Outer:
    inner: Inner
    c: float

This is supported and will serialize/deserialize correctly in Flyte tasks and workflows (Flyte dataclass docs). Would you like a full Flyte task/workflow example? Sources: - Flyte user guide: dataclass 👍 0 button 👎 0 button 💡 Hint: Mention @runllm in the thread for followups.