The task structure

Instead of plain functions, ExoSim uses a task system. A exosim.tasks.task.Task is a class that carries out one operation and, through Logger, comes with logging built in. Tasks have a fixed shape, so they can be swapped for custom versions (see Custom tasks).

Write a task

First, create a class that inherits from Task:

from exosim.tasks.task import Task

class ExampleTask(Task):
    """
    This is an example Task
    """

Then declare the inputs in __init__, with add_task_param:

def __init__(self):
    """
     Parameters
     __________
     parameters: dict
         dictionary containing the parameters. This is usually parsed from :class:`~exosim.tasks.load.load_options.LoadOptions`
     wavelength: :class:`~astropy.units.Quantity`
         wavelength grid.
     output: :class:`~exosim.output.output.Output` (optional)
        output file
     """

    self.add_task_param('parameters', 'channel parameters dict')
    self.add_task_param('wavelength', 'wavelength grid')
    self.add_task_param('output', 'output file', None)

Here the task takes three inputs: a dictionary, a wavelength grid and an output file. The last one is optional, since it is given the default value None.

Then describe what the task does, in execute:

def execute(self):
    parameters = self.get_task_param('parameters')
    wavelength = self.get_task_param('wavelength')
    output = self.get_task_param('output')

    ...

    variable = None
    self.set_output(variable)

get_task_param returns the value associated with the input name. After the work is done, the result is handed back with set_output. To return several values, pass a list:

variable1 = None
variable2 = None
self.set_output([variable1, variable2])

Logging

The Task class provides the same logging methods as Logger:

self.info("info message")
self.debug("debug message")
self.warning("warning message")
self.error("error message")
self.critical("critical message")

They can be used in any method of the task.

Use a task

Initialise the task, then call it with its parameters:

exampleTask = ExampleTask()
variable = exampleTask(parameters=par_dic, wavelength=wl_grid)