made update_period optional in Updater

A

Author: evvaaaa

src/fastcs/attributes.py

@@ -26,7 +26,8 @@ async def put(self, controller: Any, attr: AttrW, value: Any) -> None:
 class Updater(Protocol):
     """Protocol for updating the cached readback value of an ``Attribute``."""
 
-    update_period: float
+    # If update period is None then the attribute will not be updated as a task.
+    update_period: float | None
 
     async def update(self, controller: Any, attr: AttrR) -> None:
         pass
@@ -52,7 +53,7 @@ def __init__(
         group: str | None = None,
         handler: Any = None,
         allowed_values: list[T] | None = None,
-        description: str | None = None
+        description: str | None = None,
     ) -> None:
         assert (
             datatype.dtype in ATTRIBUTE_TYPES
@@ -103,7 +104,7 @@ def __init__(
             group,
             handler,
             allowed_values=allowed_values,  # type: ignore
-            description=description
+            description=description,
         )
         self._value: T = datatype.dtype()
         self._update_callback: AttrCallback[T] | None = None
@@ -136,15 +137,15 @@ def __init__(
         group: str | None = None,
         handler: Sender | None = None,
         allowed_values: list[T] | None = None,
-        description: str | None = None
+        description: str | None = None,
     ) -> None:
         super().__init__(
             datatype,  # type: ignore
             access_mode,
             group,
             handler,
             allowed_values=allowed_values,  # type: ignore
-            description=description
+            description=description,
         )
         self._process_callback: AttrCallback[T] | None = None
         self._write_display_callback: AttrCallback[T] | None = None
@@ -186,15 +187,15 @@ def __init__(
         group: str | None = None,
         handler: Handler | None = None,
         allowed_values: list[T] | None = None,
-        description: str | None = None
+        description: str | None = None,
     ) -> None:
         super().__init__(
             datatype,  # type: ignore
             access_mode,
             group,
             handler,
             allowed_values,  # type: ignore
-            description=description
+            description=description,
         )
 
     async def process(self, value: T) -> None:

src/fastcs/backend.py

@@ -137,7 +137,8 @@ def _add_attribute_updater_tasks(
                 callback = _create_updater_callback(
                     attribute, single_mapping.controller
                 )
-                scan_dict[update_period].append(callback)
+                if update_period is not None:
+                    scan_dict[update_period].append(callback)
 
 
 def _create_updater_callback(attribute, controller):