What’s the Prefectest way to use the value of a

prefect.Parameter

in a call to a

prefect.ShellTask

? Would I use a

StringFormatter

task?

Hi Jake! I could be missing something here, but is there a reason you wouldn't just pass the parameter to your

ShellTask

the same way you would with any other parameter? E.g.:

@task
def print_plus_one(x):
    print(x + 1)

with Flow('Parameterized Flow') as flow:
    x = Parameter('x', default = 2)
    print_plus_one(x=x)

My

ShellTask

needs to run

tar -zcvf {output_dir}.tar.gz {output_dir}

so I was hoping I could pass a dynamic value to

output_dir

as a

pf.Parameter

instead of needing to pass the whole command. Does that make sense?

StringFormatter

is the way to go then!

Another pattern you could use here if you don’t want to introduce a new task is subclassing the

ShellTask

and overriding the

run

method to only accept a parameter value which then formats the command located at

self.command

and passes it to

super().run(command=command)

. Let me know if you’d like me to cook up a code example for this