server.ua_variable.UaVariable

class documentation

class UaVariable(UaObject, ParentMixin[UaObject], Generic[_VariableType]):

Constructor: UaVariable(initial_value, unit, range, minimum_access_level, ...)

OPC UA Variable for use in ParameterSet, Monitoring, FinalResultData, etc.

Abstracts raw OPC UA/asyncua away and provides a simple, high-level interface.

Method	`__init__`	Cooperative constructor for a new variable instance.
Async Method	`add_reference`	Add a reference to the given `target` `UaObject`, i.e. a `Resource`.
Method	`check_range`	Check whether the given value is within the range.
Method	`clone`	Clone the variable configuration. It must be initialized before using it.
Method	`initial_value.setter`	Undocumented
Async Method	`read`	Read current value from variable.
Async Method	`read_optional`	Read current value from variable. Might be `None`.
Async Method	`remove_reference`	Remove the existing reference to the given `target` `UaObject`.
Async Method	`reset`	Reset variable to initial value.
Async Method	`set_historize`	Set the variable to `historize`.
Async Method	`set_writable`	Set the variable to `writable` externally. Internally, a variable is always writable.
Async Method	`write`	Write given `value` to this variable.
Method	`write_check`	Check whether given `value` can be written to this variable.
Instance Variable	`optional_ok`	Undocumented
Instance Variable	`ua_node`	Undocumented
Property	`initial_value`	Initial value of the variable.
Method	`_extract_value`	Undocumented
Async Method	`_get_definition`	Undocumented
Async Method	`_init`	Undocumented
Method	`_repr_items`	Undocumented
Async Method	`_ua_add_reference`	Undocumented
Async Method	`_ua_create_node`	Undocumented
Instance Variable	`_historize`	Undocumented
Instance Variable	`_initial_value`	Undocumented
Instance Variable	`_initial_value_type`	Undocumented
Instance Variable	`_range`	Undocumented
Instance Variable	`_references`	Undocumented
Instance Variable	`_unit`	Undocumented
Instance Variable	`_variant_type`	Undocumented
Instance Variable	`_writable`	Undocumented

Cooperative constructor for a new variable instance.

Parameters
initial_value:`_VariableType \| None`	The initial value of the variable. This should not be `None` for both correct type hints and correctly guessed OPC UA data type of the corresponding OPC UA variable node.
unit:`Unit \| str \| int \| ua.EUInformation \| None`	The engineering unit of the variable. Can either be an `Unit`, an integer (= OPC UA `ua.EUInformation.UnitId`, e.g. 4410708), or a string (symbol = OPC UA display name, e.g. "cm"). If provided, the range `range_` parameter is mandatory!
range:`tuple[float \| int, float \| int] \| ua.Range \| None`	Tuple containing the minimum and maximum values of the variable.
minimum_access_level:`int \| None`	Minimum access level required to write to the variable (externally via OPC UA).
writable:`bool`	Whether the variable is writable externally or not. Always writable internally.
historize:`bool`	Whether to keep a history of past values of this variable.
bypass_lock:`bool`	Whether the variable can be written to without ownership of corresponding lock.
variable_type:`type[_VariableType] \| None`	The Python type of the variable. Is only required if type cannot be determined from `initial_value`, i.e. when `None` is provided.
optional_ok:`bool`	Undocumented
name:`str \| None`	Undocumented
**kwargs	Undocumented

async def add_reference(self, target: UaObject): ¶

Add a reference to the given target UaObject, i.e. a Resource.

Defines valid values for UaObject variable types.

def check_range(self, value: _VariableType | ua.Variant | None) -> bool: ¶

Check whether the given value is within the range.

Returns
`bool`	`True` if the given value is within the range (or there is no range specified), `False` otherwise.

def clone(self, *, name: str, writable: bool | None = None) -> UaVariable[_VariableType]: ¶

Clone the variable configuration. It must be initialized before using it.

Parameters
name:`str`	The name of the variable.
writable:`bool \| None`	Override `writable` configuration in clone if not `None`.

Returns
`UaVariable[_VariableType]`	Undocumented

@initial_value.setter

def initial_value(self, value: _VariableType | ua.Variant): ¶

Undocumented

async def read(self) -> _VariableType: ¶

Read current value from variable.

Raises
`PyUaRuntimeError`	If reading an `UaObject` based variable type would result in `None` due to Null Node ID.

async def read_optional(self) -> _VariableType | None: ¶

Read current value from variable. Might be None.

async def remove_reference(self, target: UaObject): ¶

Remove the existing reference to the given target UaObject.

async def reset(self): ¶

Reset variable to initial value.

async def set_historize(self, historize: bool, *, period: timedelta = timedelta(days=7), count: int = 1000): ¶

Set the variable to historize.

Parameters
historize:`bool`	Whether the variable should be historized or not. The other parameters are ignored when `False`.
period:`timedelta`	data older than this will be deleted from the history. By default, keep the last 7 days.
count:`int`	max. number of value changes to keep in the history. `0` = no count limit

async def set_writable(self, writable: bool): ¶

Set the variable to writable externally. Internally, a variable is always writable.

async def write(self, value: _VariableType | ua.Variant | None): ¶

Write given value to this variable.

Note: None is only valid for a small set of variable types: str and UaObject based (internally OPC UA nodes)

Raises
`OutOfRangeError`	if `value` is not within the range of the variable.

def write_check(self, value: _VariableType | ua.Variant | None): ¶

Check whether given value can be written to this variable.

Raises
`OutOfRangeError`	if `value` is not within the range of the variable.

optional_ok: bool = ¶

Undocumented

ua_node = ¶

Undocumented

@property

initial_value: _VariableType = ¶

Initial value of the variable.

def _extract_value(self, value) -> _VariableType: ¶

Undocumented

@override

async def _get_definition(self) -> UaObjectDefinition: ¶

Undocumented

@lifecycle

async def _init(self) -> AsyncGenerator[None]: ¶

Undocumented

@override

def _repr_items(self) -> Iterator[tuple[str, object]]: ¶

Undocumented

async def _ua_add_reference(self, target: UaObject): ¶

Undocumented

@override

async def _ua_create_node(self, ua_location: Node, *, instantiate_optional: bool, exist_ok: bool, remove_existing: bool): ¶

Undocumented

_historize: bool = ¶

Undocumented

_initial_value: ua.Variant = ¶

Undocumented

_initial_value_type: type[_VariableType] = ¶

Undocumented

_range: tuple[float | int, float | int] | None = ¶

Undocumented

_references: set[UaObject] = ¶

Undocumented

_unit: ua.EUInformation | None = ¶

Undocumented

_variant_type = ¶

Undocumented

_writable: bool = ¶

Undocumented