It seems that Prefect doesn't support multiple return, or some Python syntax? ----------------------------------- @task def hello(x): a=1 b=2 return a, b with Flow('test flow') as flow: a, b = hello(1) #<---- 'NoneType' object is not callable hello(a) hello(b) ______________________________

Hi @Gary Liao, Prefect is building a deferred computational pipeline. That means that at the time you call the function

hello()

, Prefect isn’t running the function and doesn’t know that it’s going to return two items. Therefore, you can’t use Python unpacking assignment to unpack a and b inplace.

Thank you for replying so fast! I know the approach you provide works, but how to avoid the visualize function to grow so many "atomic" flows?

You ‘could’ build your own

GetItem

task:

class MyGetItem(Task):
    def __init__(self, key, *args, **kwargs):
        self.key = key
        super().__init__(*args, **kwargs)
    def run(self, task_result):
        return task_result[self.key]

then call as such:

hello_result = hello(1)
a = MyGetItem(0)(hello_result)
b = MyGetItem(1)(hello_result)

@emre that’s actually what Prefect is doing behind the scenes 🙂

this might be a very bad idea, but is it maybe feasible to support unpacking by overloading

__iter__

for tasks? the GetItem behavior is great but the

*

syntax is just so much prettier 🙂

This is the sort of message that results in me staying up all night 😉

that's actually what Prefect is doing behind the scenes

Oh I know, went a little source code mining for this myself 😅 Anyways, all aboard the unpacking hype train 🚂

🤓