Subject: Access to Flow Parameters within Flow attributes. Any suggestions? Best I can think of is to add the Flow parameters to new

params

fields in `current`:

class ExampleFlow(FlowSpec):
    date_key = Parameter("date_key", default="2020-07-23")
    data_path = Parameter("data_path", default="<s3://aip-example-stage/data/>")

    @datasets.input(name="train_data", path=f"{current.params.data_path}/date={current.params.date_key}")
    @step
    def start(self):
        pass

hmm that's tricky, i think that f-string would be evaluated pretty early, when ExampleFlow class definition is loaded by the python interpreter

how would it have access to

self

? Or must we introduce a

current.param

field?

yea we'd have to pass it somehow

Do you know where in the metaflow code base the "params" are parsed? Where and how I could set

current.params

🙂

parameters.py

i believe

hmm... this is tough: maybe evaluate later! without the f-string:

path="{current.params.data_path}/date={current.params.date_key}"

yeah that's probably the easiest/least invasive. The substitution can even be done by the

datasets.input

implementation in this case. That is, it would be part of

datasets.input

contract (not general Metaflow decorator contract) that you can a template string as a

path

parameter and it'll do parameter substitution there

then it can use

path="{self.params.data_path}"