Probably a stupid question how do I get the value of a `Para

Question

Probably a stupid question how do I get the value of a `Parameter` My use case is building a shell command ``` data source id = Parameter data source id t = shell task command=f some script data source id ```

Jeremiah · Answer

Not a stupid question slightly smiling face There are two ways

Jeremiah · Answer

The first is to use the `Parameter` as the input to a different task In your case you might need to use a `StringFormatter` see <https docs prefect io api latest tasks strings html string templating tasks|docs> to have a task to pass the value to ``` create the task fmt = StringFormatter template= some script data source id with Flow test as flow did = Parameter did pass the parameter to the string formatter string = fmt data source id=did pass the string to the shell task shell task cmd=string ```

Jeremiah · Answer

Sorry I didn t test that code but the rough idea is if you pass a `Parameter` to any other task it s value becomes the keyword argument input to that task

Jeremiah · Answer

The second way is that at runtime the parameter values are available in `prefect context get parameters ` so you can template the string with that context value However you need to make sure you apply the string template at runtime and not task initialization

Jeremiah · Answer

Both ways differ from your current implementation in that the string interpolation must take place at runtime inside a `Task` because that s the only environment that has access to the Parameter value

Manuel Aristarán · Answer

Right So would this work ```with Flow as f shell task cmd=f some script prefect context get parameters data source id ```

Manuel Aristarán · Answer

yea ugly

Jeremiah · Answer

No unfortunately `prefect context ` isn t populated until you call `flow run ` so that code will fail to load the parameter value

Manuel Aristarán · Answer

Perfect I ll go with the template slightly smiling face

Jeremiah · Answer

The `StringFormatter` s job is to take what you did there which would happen during flow definition and make it possible to do at runtime instead

Jeremiah · Answer

yes

Manuel Aristarán · Answer

Thanks a lot

Jeremiah · Answer

Let us know if that works

Manuel Aristarán · Answer

it did slightly smiling face thanks again

Jan Feřtek · Answer

Hi I can t get it working What am I missing ```from prefect import task Flow Parameter from prefect tasks templates import StringFormatter from prefect tasks shell import ShellTask msg task = StringFormatter template= my string shell task = ShellTask with Flow string template as flow name = Parameter name msg output = msg task my string=name shell output static = shell task command=f echo Arthur shell output dynamic = shell task command=f echo msg output flow state = flow run name= Marvin print flow state result msg output result Marvin print flow state result shell output static result Arthur print flow state result shell output dynamic result Command failed with exit code 2```

nicholas · Answer

Hi < Jan Feřtek> would you mind starting a new thread so we don t send alerts to people that don t need them Thanks pray

Jan Feřtek · Answer

< nicholas> Done