Hello 👋 I would love to use Parameter and mypy together. However currently when I do;

var: str = Parameter('var')

mypy complains with

Incompatible types in assignment (expression has type "Parameter", variable has type "str")

Even though after calling this will be a string 🤔 Any thoughts on how to achieve this?

If you do this in a

with Flow(name) as flow:

context, the returned value will actually not be a string but a task... We didnt implement type checking on tasks/parameters though, so I'm not sure how to solve it.

Hi @Alexander van Eck, this can be tricky. Because of deferred execution of course mypy is correct,

var

IS a

Parameter

until it's evaluated at flow run time. A couple possibilities I can think of 1. use a union of types

var: Union[str, Parameter] = Parameter('var')

2. tell mypy to ignore it

var: str = Parameter('var') # type: ignore

We're working on some features that will allow Parameter typing (and enforcement of typing!!) in the future.

Great to hear @Zach Angell 🙂 I’ve gone with

cast

where necessary. but it looks like when passing Parameter into a prefect task it actually doesn’t complain! Just when using Parameter directly