3. Entry Points

Entry Points are like the verbs that your App can do. The built-in entry points offer basic functionality, like running a case or opening up the GUI, but the real joy of an application comes when you add your own project-specific entry points that do the actions that you commonly need done.

To make a new EntryPoint, first make a new module and subclass EntryPoint. Set the class attributes as follows:

name

What the user types on the CLI to invoke this entry point.

settingsArgument

• "required" if a settings input file must be provided,

• "optional" if it may be provided but not required,

• None if no settings input is allowed

Tip

ARMI apps often collect EntryPoints in a cli/ directory (Command Line Interface)

Next, implement the addOptions() method. Here you can both:

• turn various Settings into command-line arguments with createOptionFromSetting()

• add arbitrary command-line arguments using the standard argparse library.

The values of the non-setting arguments will become attributes in self.args for later use.

Finally, implement the invoke() method with the code you’d like to run upon invocation of this entry point.

Example entry point

from armi.cli import entryPoint

class SampleEntryPoint(entryPoint.EntryPoint):
    """
    Entry point title here

    Long description of entry point here. This will actually get picked up and used
    as the help text on the command line itself!
    """

    name = "do-my-thing"
    settingsArgument = "required"

    def addOptions(self):
        self.createOptionFromSetting(CONF_CYCLE_LENGTH)
        self.createOptionFromSetting(CONF_BURN_STEPS)
        self.parser.add_argument(
            "--post-process",
            "-p",
            action="store_true",
            default=False,
            help="Just post-process an existing suite; don't run",
        )

    def invoke(self):
        from armi import cases

        inputCase = cases.Case(cs=self.cs)
        print(f"The case is {inputCase}")

        if self.args.post_process:
            print("Post processing...")

When you run your app, you will have this as an option, and you can invoke it with:

python -m myapp do-my-thing --post-process settingsFile.yaml

or (if myapp is not in your PYTHONPATH):

python path/to/myapp do-my-thing --post-process settingsFile.yaml

Tip

The settings file will be read into a Settings object. This Settings object will be passed widely around the code. Please do not edit these settings during a run. The idea of “run settings” is a lot simpler to understand when they don’t change. And such changes tend to hide data from other developers.