Class: QgsVectorLayerFeatureCounter

class qgis.core.QgsVectorLayerFeatureCounter

Bases: QgsTask

Counts the features in a QgsVectorLayer in task. You should most likely not use this directly and instead call QgsVectorLayer.countSymbolFeatures() and connect to the signal QgsVectorLayer.symbolFeatureCountMapChanged().

New in version 3.0.

QgsVectorLayerFeatureCounter(layer: QgsVectorLayer, context: QgsExpressionContext = QgsExpressionContext(), storeSymbolFids: bool = False) Create a new feature counter for layer.

Parameters

• layer – Target QgsVectorLayer to perform counting on.

• context – Specific QgsExpressionContext to use during the rendering step.

• storeSymbolFids –

  If True will store the feature ids (fids), otherwise will only count the number of features per symbol. Default False.

  Methods

  cancel
  childEvent
  connectNotify
  customEvent
  disconnectNotify
  featureCount	Returns the feature count for a particular legendKey.
  featureIds	Returns the feature Ids for a particular legendKey.
  finished	If the task is managed by a QgsTaskManager, this will be called after the task has finished (whether through successful completion or via early termination).
  isCanceled	Will return True if task should terminate ASAP.
  isSignalConnected
  receivers
  run	Calculates the feature count and Ids per symbol
  sender
  senderSignalIndex
  setProgress	Sets the task's current progress.
  timerEvent

  Signals

  symbolsCounted

  Emitted when the symbols have been counted.

cancel(self)

childEvent(self, QChildEvent)

connectNotify(self, QMetaMethod)

customEvent(self, QEvent)

disconnectNotify(self, QMetaMethod)

featureCount(self, legendKey: str) → int

Returns the feature count for a particular legendKey. If the key has not been found, -1 will be returned.

Parameters

legendKey (str) –

Return type

int

featureIds(self, symbolkey: str) → object

Returns the feature Ids for a particular legendKey. If the key has not been found an empty QSet will be returned.

New in version 3.10.

Parameters

symbolkey (str) –

Return type

object

finished(self, result: bool)

If the task is managed by a QgsTaskManager, this will be called after the task has finished (whether through successful completion or via early termination). The result argument reflects whether the task was successfully completed or not. This method is always called from the main thread, so it is safe to create widgets and perform other operations which require the main thread. However, the GUI will be blocked for the duration of this method so tasks should avoid performing any lengthy operations here.

isCanceled(self) → bool

Will return True if task should terminate ASAP. If the task reports the CanCancel flag, then derived classes’ run() methods should periodically check this and terminate in a safe manner.

isSignalConnected(self, QMetaMethod) → bool

receivers(self, PYQT_SIGNAL) → int

run(self) → bool

Calculates the feature count and Ids per symbol

Return type

bool

sender(self) → QObject

senderSignalIndex(self) → int

setProgress(self, progress: float)

Sets the task’s current progress. The derived class should call this method whenever the task wants to update its progress. Calling will automatically emit the progressChanged signal.

Parameters

progress – percent of progress, from 0.0 - 100.0

symbolsCounted

Emitted when the symbols have been counted. [signal]

timerEvent(self, QTimerEvent)