lsst.pipe.base.task.Task Class Reference

Base class for data processing tasks. More...

Inheritance diagram for lsst.pipe.base.task.Task:

Public Member Functions
def	__init__
	Create a Task. More...
def	emptyMetadata
	Empty (clear) the metadata for this Task and all sub-Tasks. More...
def	getSchemaCatalogs
	Return the schemas generated by this task. More...
def	getAllSchemaCatalogs
	Call getSchemaCatalogs() on all tasks in the hiearchy, combining the results into a single dict. More...
def	getFullMetadata
	Get metadata for all tasks. More...
def	getFullName
	Return the task name as a hierarchical name including parent task names. More...
def	getName
	Return the name of the task. More...
def	getTaskDict
	Return a dictionary of all tasks as a shallow copy. More...
def	makeSubtask
	Create a subtask as a new instance self. More...
def	timer
	Context manager to log performance data for an arbitrary block of code. More...
def	display
	Display an exposure and/or sources. More...
def	makeField
	Make an lsst.pex.config.ConfigurableField for this task. More...

Public Attributes
	metadata
	config
	log

Private Member Functions
def	_computeFullName
	Compute the full name of a subtask or metadata item, given its brief name. More...

Private Attributes
	_name
	_fullName
	_taskDict
	_display

Detailed Description

Base class for data processing tasks.

See pipe_base introduction to learn what tasks are, and how to write a task for more information about writing tasks. If the second link is broken (as it will be before the documentation is cross-linked) then look at the main page of pipe_tasks documentation for a link.

Useful attributes include:

• log: an lsst.pex.logging.Log
• config: task-specific configuration; an instance of ConfigClass (see below)
• metadata: an lsst.daf.base.PropertyList for collecting task-specific metadata, e.g. data quality and performance metrics. This is data that is only meant to be persisted, never to be used by the task.

Subclasses typically have a method named "run" to perform the main data processing. Details:

• run should process the minimum reasonable amount of data, typically a single CCD. Iteration, if desired, is performed by a caller of the run method. This is good design and allows multiprocessing without the run method having to support it directly.
• If "run" can persist or unpersist data:
  • "run" should accept a butler data reference (or a collection of data references, if appropriate, e.g. coaddition).
  • There should be a way to run the task without persisting data. Typically the run method returns all data, even if it is persisted, and the task's config method offers a flag to disable persistence.

Deprecated:

Tasks other than cmdLineTask.CmdLineTasks should not accept a blob such as a butler data reference. How we will handle data references is still TBD, so don't make changes yet! RHL 2014-06-27

Subclasses must also have an attribute ConfigClass that is a subclass of lsst.pex.config.Config which configures the task. Subclasses should also have an attribute _DefaultName: the default name if there is no parent task. _DefaultName is required for subclasses of CmdLineTask and recommended for subclasses of Task because it simplifies construction (e.g. for unit tests).

Tasks intended to be run from the command line should be subclasses of CmdLineTask, not Task.

Definition at line 73 of file task.py.

Constructor & Destructor Documentation

def lsst.pipe.base.task.Task.__init__	(		self,
			config = None,
			name = None,
			parentTask = None,
			log = None
	)

Create a Task.

Parameters

[in]	config	configuration for this task (an instance of self.ConfigClass, which is a task-specific subclass of lsst.pex.config.Config), or None. If None: If parentTask specified then defaults to parentTask.config.<name> If parentTask is None then defaults to self.ConfigClass()
[in]	name	brief name of task, or None; if None then defaults to self._DefaultName
[in]	parentTask	the parent task of this subtask, if any. If None (a top-level task) then you must specify config and name is ignored. If not None (a subtask) then you must specify name
[in]	log	pexLog log; if None then the default is used; in either case a copy is made using the full task name.

Exceptions

RuntimeError	if parentTask is None and config is None.
RuntimeError	if parentTask is not None and name is None.
RuntimeError	if name is None and _DefaultName does not exist.

Definition at line 110 of file task.py.

    def __init__(self, config=None, name=None, parentTask=None, log=None):
        """!Create a Task
        
        @param[in] config       configuration for this task (an instance of self.ConfigClass,
            which is a task-specific subclass of lsst.pex.config.Config), or None. If None:
            - If parentTask specified then defaults to parentTask.config.<name>
            - If parentTask is None then defaults to self.ConfigClass()
        @param[in] name         brief name of task, or None; if None then defaults to self._DefaultName
        @param[in] parentTask   the parent task of this subtask, if any.
            - If None (a top-level task) then you must specify config and name is ignored.
            - If not None (a subtask) then you must specify name
        @param[in] log          pexLog log; if None then the default is used;
            in either case a copy is made using the full task name.
        
        @throw RuntimeError if parentTask is None and config is None.
        @throw RuntimeError if parentTask is not None and name is None.
        @throw RuntimeError if name is None and _DefaultName does not exist.
        """
        self.metadata = dafBase.PropertyList()

        if parentTask != None:
            if name is None:
                raise RuntimeError("name is required for a subtask")
            self._name = name
            self._fullName = parentTask._computeFullName(name)
            if config == None:
                config = getattr(parentTask.config, name)
            self._taskDict = parentTask._taskDict
        else:
            if name is None:
                name = getattr(self, "_DefaultName", None)
                if name is None:
                    raise RuntimeError("name is required for a task unless it has attribute _DefaultName")
                name = self._DefaultName
            self._name = name
            self._fullName = self._name
            if config == None:
                config = self.ConfigClass()
            self._taskDict = dict()
  
        self.config = config
        if log == None:
            log = pexLog.getDefaultLog()
        self.log = pexLog.Log(log, self._fullName)
        self._display = lsstDebug.Info(self.__module__).display
        self._taskDict[self._fullName] = self