The Task structure

Instead of functions, ExoSim uses a tasks system. The exosim.tasks.task.Task is a class with logging properties (from Logger) which executes some operations.

Write a Task

To write a task, first we need to create a class that inherits from the Task class:

from exosim.tasks.task import Task

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

Then we need to define the inputs. This must be done in the class __init__ using the add_task_param method:

def __init__(self):
    """
     Parameters
     __________
     parameters: dict
         dictionary containing the parameters. This is usually parsed from :class:`~exosim.tasks.load.loadOptions.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)

In this example we want the task to have 3 inputs: a dictionary, a wavelength grid and an output file. The latter is optional, in fact we have set None as a default value.

Then we can move to describe the operations that this Task is gonna do:

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

    ...

    variable = None
    self.set_output(variable)

The get_task_param method allow to retrieve the variable associated to the string used as argument. Then some operations are done and the output is set with the set_output method. If a list of variables are expected as output the code will be

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

Logging

Logging is important when producing a new task, hence we include some logging options into the Task class. Here are some examples of how to use them, but you can have a better understanding by looking at the Logger class.

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

These lines can be include in every method inside the Task class.

Use a Task

To use a Task we first need to initialise it, and the call it with it’s parameters:

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