Dynamic Static Inputs

The title of this page is a perfectly legit oxymoron in StepUp: it is possible to declare a static input file and then amend the same step with that file as a dynamic input, all in the same script. It is a special case of Dynamic Dependencies, which is occasionally useful. As of StepUp 1.2.0, this is allowed and no longer treated as a cyclic dependency.

For example, plan.py may read a configuration file to decide which steps to add to the workflow. Hence, the config file is a static input to the workflow. Since StepUp schedules the top-level ./plan.py step without initial inputs, you have to use amend() to inform StepUp of this dependency. Whenever you change the config file, StepUp will re-run ./plan.py to update the workflow.

Example

Create the following plan.py, which declares a static file, amends the step with that file as a dynamic input, and then opens it to print it to the standard output.

#!/usr/bin/env python3
from stepup.core.api import amend, static

static("config.txt")
amend(inp="config.txt")
with open("config.txt") as fh:
    print(fh.read().strip())

Also create a config.txt file with some contents.

In more realistic scenarios, config.txt may be used to decide which steps to add etc. For a more elaborate example, take a look at the plan.py that is used to run all tutorial examples.

Make plan.py executable and run it as follows:

chmod +x plan.py
sb -j 1

You should get the following terminal output:

DIRECTOR │ Listening on /tmp/stepup-########/director (StepUp Core 4.0.0)
 STARTUP │ (Re)initialized boot script
   PHASE │ build
   START │ ./plan.py
 SUCCESS │ ./plan.py
─────────────────────────────── Standard output ────────────────────────────────
This is a config file.
────────────────────────────────────────────────────────────────────────────────
DIRECTOR │ Ran 1 job(s).
DIRECTOR │ Trying to remove 0 deletable file(s) and empty director(y|ies)
DIRECTOR │ See you!