Parameter tree

parameter_tree.py - classes representing a sychronous parameter tree and accessor.

This module defines a parameter tree and accessor for use in synchronous API adapters, where concurrency over blocking operations (e.g. to read/write the value of a parameter from hardware) is not required.

Tim Nicholls, STFC Detector Systems Software Group.

ParameterAccessor

Bases: BaseParameterAccessor

Synchronous container class representing accessor methods for a parameter.

This class extends the base parameter accessor class to support synchronous set and get accessors for a parameter. Read-only and writeable parameters are supported, and the same metadata fields are implemented.

Source code in src/odin_control/adapters/parameter_tree.py

class ParameterAccessor(BaseParameterAccessor):
    """Synchronous container class representing accessor methods for a parameter.

    This class extends the base parameter accessor class to support synchronous set and get
    accessors for a parameter. Read-only and writeable parameters are supported, and the same
    metadata fields are implemented.
    """

    def __init__(self, path, getter=None, setter=None, **kwargs):
        """Initialise the ParameterAccessor instance.

        This constructor initialises the ParameterAccessor instance, storing the path of the
        parameter, its set/get accessors and setting metadata fields based on the the specified
        keyword arguments.

        :param path: path of the parameter within the tree
        :param getter: get method for the parameter, or a value if read-only constant
        :param setter: set method for the parameter
        :param kwargs: keyword argument list for metadata fields to be set; these must be from
                       the allow list specified in BaseParameterAccessor.allowed_metadata
        """
        # Initialise the superclass with the specified arguments
        super(ParameterAccessor, self).__init__(path, getter, setter, **kwargs)

        # Save the type of the parameter for type checking
        self._type = type(self.get())

        # Set the type metadata fields based on the resolved tyoe
        self.metadata["type"] = self._type.__name__

__init__(path, getter=None, setter=None, **kwargs)

Initialise the ParameterAccessor instance.

This constructor initialises the ParameterAccessor instance, storing the path of the parameter, its set/get accessors and setting metadata fields based on the the specified keyword arguments.

Parameters:

Name	Type	Description	Default
path		path of the parameter within the tree	required
getter		get method for the parameter, or a value if read-only constant	None
setter		set method for the parameter	None
kwargs		keyword argument list for metadata fields to be set; these must be from the allow list specified in BaseParameterAccessor.allowed_metadata	{}

Source code in src/odin_control/adapters/parameter_tree.py

def __init__(self, path, getter=None, setter=None, **kwargs):
    """Initialise the ParameterAccessor instance.

    This constructor initialises the ParameterAccessor instance, storing the path of the
    parameter, its set/get accessors and setting metadata fields based on the the specified
    keyword arguments.

    :param path: path of the parameter within the tree
    :param getter: get method for the parameter, or a value if read-only constant
    :param setter: set method for the parameter
    :param kwargs: keyword argument list for metadata fields to be set; these must be from
                   the allow list specified in BaseParameterAccessor.allowed_metadata
    """
    # Initialise the superclass with the specified arguments
    super(ParameterAccessor, self).__init__(path, getter, setter, **kwargs)

    # Save the type of the parameter for type checking
    self._type = type(self.get())

    # Set the type metadata fields based on the resolved tyoe
    self.metadata["type"] = self._type.__name__

ParameterTree

Bases: BaseParameterTree

Class implementing a synchronous tree of parameters and their accessors.

This lass implements an arbitrarily-structured, recursively-managed tree of parameters and the appropriate accessor methods that are used to read and write those parameters.

Source code in src/odin_control/adapters/parameter_tree.py

class ParameterTree(BaseParameterTree):
    """Class implementing a synchronous tree of parameters and their accessors.

    This lass implements an arbitrarily-structured, recursively-managed tree of parameters
    and the appropriate accessor methods that are used to read and write those parameters.
    """

    def __init__(self, tree, mutable=False):
        """Initialise the ParameterTree object.

        This constructor recursively initialises the ParameterTree object based on the specified
        arguments. The tree initialisation syntax follows that of the BaseParameterTree
        implementation.

        :param tree: dict representing the parameter tree
        :param mutable: Flag, setting the tree
        """
        # Set the accessor class used by this tree to ParameterAccessor
        self.accessor_cls = ParameterAccessor

        # Initialise the superclass with the speccified parameters
        super(ParameterTree, self).__init__(tree, mutable)

__init__(tree, mutable=False)

Initialise the ParameterTree object.

This constructor recursively initialises the ParameterTree object based on the specified arguments. The tree initialisation syntax follows that of the BaseParameterTree implementation.

Parameters:

Name	Type	Description	Default
tree		dict representing the parameter tree	required
mutable		Flag, setting the tree	False

Source code in src/odin_control/adapters/parameter_tree.py

def __init__(self, tree, mutable=False):
    """Initialise the ParameterTree object.

    This constructor recursively initialises the ParameterTree object based on the specified
    arguments. The tree initialisation syntax follows that of the BaseParameterTree
    implementation.

    :param tree: dict representing the parameter tree
    :param mutable: Flag, setting the tree
    """
    # Set the accessor class used by this tree to ParameterAccessor
    self.accessor_cls = ParameterAccessor

    # Initialise the superclass with the speccified parameters
    super(ParameterTree, self).__init__(tree, mutable)

ParameterTreeError

Bases: Exception

Simple error class for raising parameter tree parameter tree exceptions.

Source code in src/odin_control/adapters/base_parameter_tree.py

class ParameterTreeError(Exception):
    """Simple error class for raising parameter tree parameter tree exceptions."""

    pass