Class: QgsExpressionSelectionDialog

A dialog for selecting features by expression.

To do so, a QgsExpressionBuilderWidget is shown in a dialog. It offers the possibilities to create a new selection, add to the current selection remove from the current selection or select within the current selection.

Class Hierarchy

Base classes

QDialog
QWidget
QObject
QPaintDevice

Methods

expressionBuilder	The builder widget that is used by the dialog
expressionText	Returns the current expression text
setExpressionText	Sets the current expression text
setGeomCalculator	Sets geometry calculator used in distance/area calculations.
setMapCanvas	Sets a map canvas associated with the dialog.
setMessageBar	Sets the message bar to display feedback from the dialog.

Virtual Methods

In PyQGIS, only methods marked as virtual can be safely overridden in a Python subclass of QgsExpressionSelectionDialog. See the FAQ for more details.

closeEvent	Implementation for closeEvent Saves the window geometry
done	Implementation for done (default behavior when pressing esc) Calls close, so the window geometry gets saved and the object deleted.

class qgis.gui.QgsExpressionSelectionDialog

Bases: QDialog

__init__(layer: QgsVectorLayer | None, startText: str | None = '', parent: QWidget | None = None)

Creates a new selection dialog.

Parameters:

• layer (Optional[QgsVectorLayer]) – The layer on which the selection is to be performed.

• startText (Optional[str] = '') – A default expression text to be applied (Defaults to empty)

• parent (Optional[QWidget] = None) – parent object (owner)

virtual closeEvent(self, closeEvent: QCloseEvent | None)

Implementation for closeEvent Saves the window geometry

Parameters:

closeEvent (Optional[QCloseEvent]) – Event object. Unused.

virtual done(self, r: int)

Implementation for done (default behavior when pressing esc) Calls close, so the window geometry gets saved and the object deleted.

Parameters:

r (int) – Result value. Unused.

expressionBuilder(self) → QgsExpressionBuilderWidget | None

The builder widget that is used by the dialog

Return type:

Optional[QgsExpressionBuilderWidget]

Returns:

The builder widget that is used by the dialog

expressionText(self) → str

Returns the current expression text

Return type:

str

Returns:

The expression text

setExpressionText(self, text: str | None)

Sets the current expression text

Parameters:

text (Optional[str]) – the expression text to set

setGeomCalculator(self, da: QgsDistanceArea)

Sets geometry calculator used in distance/area calculations.

Parameters:

da (QgsDistanceArea)

setMapCanvas(self, canvas: QgsMapCanvas | None)

Sets a map canvas associated with the dialog.

Parameters:

canvas (Optional[QgsMapCanvas])

setMessageBar(self, messageBar: QgsMessageBar | None)

Sets the message bar to display feedback from the dialog. This is used when zooming to features to display the count of selected features.

Parameters:

messageBar (Optional[QgsMessageBar]) – target message bar