Class: QgsTaskManager

Task manager for managing a set of long-running QgsTask tasks.

This class can be created directly, or accessed via QgsApplication.taskManager().

Class Hierarchy

Base classes

QObject

Methods

activeTasks	Returns a list of the active (queued or running) tasks.
addTask	Adds a task to the manager.
cancelAll	Instructs all tasks tracked by the manager to terminate.
count	Returns the number of tasks tracked by the manager.
countActiveTasks	Returns the number of active (queued or running) tasks.
dependenciesSatisfied	Returns True if all dependencies for the specified task are satisfied
dependentLayers	Returns a list of layers on which as task is dependent.
task	Returns the task with matching ID.
taskId	Returns the unique task ID corresponding to a task managed by the class.
tasks	Returns all tasks tracked by the manager.
tasksDependentOnLayer	Returns a list of tasks which depend on a layer.
threadPool	Returns the threadpool utilized by the task manager.
triggerTask	Triggers a task, e.g. as a result of a GUI interaction.

Signals

allTasksFinished	Emitted when all tasks are complete
countActiveTasksChanged	Emitted when the number of active tasks changes
finalTaskProgressChanged	Will be emitted when only a single task remains to complete and that task has reported a progress change
progressChanged	Will be emitted when a task reports a progress change
statusChanged	Will be emitted when a task reports a status change
taskAboutToBeDeleted	Emitted when a task is about to be deleted
taskAdded	Emitted when a new task has been added to the manager
taskTriggered	Emitted when a task is triggered.

class qgis.core.QgsTaskManager

Bases: QObject

__init__(parent: QObject | None = None)

Constructor for QgsTaskManager.

Parameters:

parent (Optional[QObject] = None) – parent QObject

class TaskDefinition

Bases: object

Definition of a task for inclusion in the manager.

dependentTasks: QgsTaskList

List of dependent tasks which must be completed before task can run. If any dependent tasks are canceled this task will also be canceled. Dependent tasks must also be added to the task manager for proper handling of dependencies.

task: QgsTask

Task

activeTasks(self) → List[QgsTask]

Returns a list of the active (queued or running) tasks.

See also

countActiveTasks()

Return type:

List[QgsTask]

addTask(self, task: QgsTask | None, priority: int = 0) → int

Adds a task to the manager. Ownership of the task is transferred to the manager, and the task manager will be responsible for starting the task. The priority argument can be used to control the run queue’s order of execution, with larger numbers taking precedence over lower priority numbers.

Return type:

int

Returns:

unique task ID, or 0 if task could not be added

Parameters:

• task (Optional[QgsTask])

• priority (int = 0)

addTask(self, task: QgsTaskManager.TaskDefinition, priority: int = 0) → int

Adds a task to the manager, using a full task definition (including dependency handling). Ownership of the task is transferred to the manager, and the task manager will be responsible for starting the task. The priority argument can be used to control the run queue’s order of execution, with larger numbers taking precedence over lower priority numbers.

Return type:

int

Returns:

unique task ID, or 0 if task could not be added

Parameters:

• task (QgsTaskManager.TaskDefinition)

• priority (int = 0)

signal allTasksFinished

Emitted when all tasks are complete

See also

countActiveTasksChanged()

cancelAll(self)

Instructs all tasks tracked by the manager to terminate. Individual tasks may take some time to cancel, or may totally ignore this instruction. Calling this does not block but will instead signal the tasks to cancel and then return immediately.

count(self) → int

Returns the number of tasks tracked by the manager.

Return type:

int

countActiveTasks(self, includeHidden: bool = True) → int

Returns the number of active (queued or running) tasks.

The includeHidden argument dictates whether hidden tasks should be shown.

See also

activeTasks()

See also

countActiveTasksChanged()

Parameters:

includeHidden (bool = True)

Return type:

int

signal countActiveTasksChanged(count: int)

Emitted when the number of active tasks changes

See also

countActiveTasks()

Parameters:

count (int)

dependenciesSatisfied(self, taskId: int) → bool

Returns True if all dependencies for the specified task are satisfied

Parameters:

taskId (int)

Return type:

bool

dependentLayers(self, taskId: int) → List[QgsMapLayer]

Returns a list of layers on which as task is dependent. The task will automatically be canceled if any of these layers are about to be removed.

Parameters:

taskId (int) – task ID

Return type:

List[QgsMapLayer]

Returns:

list of layers

See also

tasksDependentOnLayer()

signal finalTaskProgressChanged(progress: float)

Will be emitted when only a single task remains to complete and that task has reported a progress change

Parameters:

progress (float) – percent of progress, from 0.0 - 100.0

signal progressChanged(taskId: int, progress: float)

Will be emitted when a task reports a progress change

Parameters:

• taskId (int) – ID of task

• progress (float) – percent of progress, from 0.0 - 100.0

signal statusChanged(taskId: int, status: int)

Will be emitted when a task reports a status change

Parameters:

• taskId (int) – ID of task

• status (int) – new task status

task(self, id: int) → QgsTask | None

Returns the task with matching ID.

Parameters:

id (int) – task ID

Return type:

Optional[QgsTask]

Returns:

task if found, or None

signal taskAboutToBeDeleted(taskId: int)

Emitted when a task is about to be deleted

Parameters:

taskId (int) – ID of task

signal taskAdded(taskId: int)

Emitted when a new task has been added to the manager

Parameters:

taskId (int) – ID of task

taskId(self, task: QgsTask | None) → int

Returns the unique task ID corresponding to a task managed by the class.

Parameters:

task (Optional[QgsTask]) – task to find

Return type:

int

Returns:

task ID, or -1 if task not found

signal taskTriggered(task: QgsTask)

Emitted when a task is triggered. This occurs when a user clicks on the task from the QGIS GUI, and can be used to show detailed progress reports or re-open a related dialog.

See also

triggerTask()

Parameters:

task (QgsTask)

tasks(self) → List[QgsTask]

Returns all tasks tracked by the manager.

Return type:

List[QgsTask]

tasksDependentOnLayer(self, layer: QgsMapLayer | None) → List[QgsTask]

Returns a list of tasks which depend on a layer.

See also

dependentLayers()

Parameters:

layer (Optional[QgsMapLayer])

Return type:

List[QgsTask]

threadPool(self) → QThreadPool | None

Returns the threadpool utilized by the task manager.

Added in version 3.34.

Return type:

Optional[QThreadPool]

triggerTask(self, task: QgsTask | None)

Triggers a task, e.g. as a result of a GUI interaction.

See also

taskTriggered()

Parameters:

task (Optional[QgsTask])