PipelineTaskConnections is a class used to declare desired IO when a
PipelineTask is run by an activator
Parameters
----------
config : `PipelineTaskConfig`
A `PipelineTaskConfig` class instance whose class has been configured
to use this `PipelineTaskConnectionsClass`
Notes
-----
``PipelineTaskConnection`` classes are created by declaring class
attributes of types defined in `lsst.pipe.base.connectionTypes` and are
listed as follows:
* ``InitInput`` - Defines connections in a quantum graph which are used as
inputs to the ``__init__`` function of the `PipelineTask` corresponding
to this class
* ``InitOuput`` - Defines connections in a quantum graph which are to be
persisted using a butler at the end of the ``__init__`` function of the
`PipelineTask` corresponding to this class. The variable name used to
define this connection should be the same as an attribute name on the
`PipelineTask` instance. E.g. if an ``InitOutput`` is declared with
the name ``outputSchema`` in a ``PipelineTaskConnections`` class, then
a `PipelineTask` instance should have an attribute
``self.outputSchema`` defined. Its value is what will be saved by the
activator framework.
* ``PrerequisiteInput`` - An input connection type that defines a
`lsst.daf.butler.DatasetType` that must be present at execution time,
but that will not be used during the course of creating the quantum
graph to be executed. These most often are things produced outside the
processing pipeline, such as reference catalogs.
* ``Input`` - Input `lsst.daf.butler.DatasetType` objects that will be used
in the ``run`` method of a `PipelineTask`. The name used to declare
class attribute must match a function argument name in the ``run``
method of a `PipelineTask`. E.g. If the ``PipelineTaskConnections``
defines an ``Input`` with the name ``calexp``, then the corresponding
signature should be ``PipelineTask.run(calexp, ...)``
* ``Output`` - A `lsst.daf.butler.DatasetType` that will be produced by an
execution of a `PipelineTask`. The name used to declare the connection
must correspond to an attribute of a `Struct` that is returned by a
`PipelineTask` ``run`` method. E.g. if an output connection is
defined with the name ``measCat``, then the corresponding
``PipelineTask.run`` method must return ``Struct(measCat=X,..)`` where
X matches the ``storageClass`` type defined on the output connection.
The process of declaring a ``PipelineTaskConnection`` class involves
parameters passed in the declaration statement.
The first parameter is ``dimensions`` which is an iterable of strings which
defines the unit of processing the run method of a corresponding
`PipelineTask` will operate on. These dimensions must match dimensions that
exist in the butler registry which will be used in executing the
corresponding `PipelineTask`.
The second parameter is labeled ``defaultTemplates`` and is conditionally
optional. The name attributes of connections can be specified as python
format strings, with named format arguments. If any of the name parameters
on connections defined in a `PipelineTaskConnections` class contain a
template, then a default template value must be specified in the
``defaultTemplates`` argument. This is done by passing a dictionary with
keys corresponding to a template identifier, and values corresponding to
the value to use as a default when formatting the string. For example if
``ConnectionClass.calexp.name = '{input}Coadd_calexp'`` then
``defaultTemplates`` = {'input': 'deep'}.
Once a `PipelineTaskConnections` class is created, it is used in the
creation of a `PipelineTaskConfig`. This is further documented in the
documentation of `PipelineTaskConfig`. For the purposes of this
documentation, the relevant information is that the config class allows
configuration of connection names by users when running a pipeline.
Instances of a `PipelineTaskConnections` class are used by the pipeline
task execution framework to introspect what a corresponding `PipelineTask`
will require, and what it will produce.
Examples
--------
>>> from lsst.pipe.base import connectionTypes as cT
>>> from lsst.pipe.base import PipelineTaskConnections
>>> from lsst.pipe.base import PipelineTaskConfig
>>> class ExampleConnections(PipelineTaskConnections,
... dimensions=("A", "B"),
... defaultTemplates={"foo": "Example"}):
... inputConnection = cT.Input(doc="Example input",
... dimensions=("A", "B"),
... storageClass=Exposure,
... name="{foo}Dataset")
... outputConnection = cT.Output(doc="Example output",
... dimensions=("A", "B"),
... storageClass=Exposure,
... name="{foo}output")
>>> class ExampleConfig(PipelineTaskConfig,
... pipelineConnections=ExampleConnections):
... pass
>>> config = ExampleConfig()
>>> config.connections.foo = Modified
>>> config.connections.outputConnection = "TotallyDifferent"
>>> connections = ExampleConnections(config=config)
>>> assert(connections.inputConnection.name == "ModifiedDataset")
>>> assert(connections.outputConnection.name == "TotallyDifferent")
Definition at line 260 of file connections.py.