Class: QgsExpressionContextUtils¶

class qgis.core.QgsExpressionContextUtils¶

Bases: sip.wrapper

Contains utilities for working with QgsExpressionContext objects, including methods for creating scopes for specific uses (e.g., project scopes, layer scopes).

New in version 2.12: Enums

Methods

`atlasScope`	Creates a new scope which contains variables and functions relating to a `QgsLayoutAtlas`.
`createFeatureBasedContext`	Helper function for creating an expression context which contains just a feature and fields collection.
`formScope`	Creates a new scope which contains functions and variables from the current attribute form/table `feature`.
`globalProjectLayerScopes`	Creates a list of three scopes: global, layer’s project and layer.
`globalScope`	Creates a new scope which contains variables and functions relating to the global QGIS context.
`layerScope`	Creates a new scope which contains variables and functions relating to a `QgsMapLayer`.
`layoutItemScope`	Creates a new scope which contains variables and functions relating to a `QgsLayoutItem`.
`layoutScope`	Creates a new scope which contains variables and functions relating to a `QgsLayout` `layout`.
`mapSettingsScope`	Creates a new scope which contains variables and functions relating to a QgsMapSettings object.
`mapToolCaptureScope`	Sets the expression context variables which are available for expressions triggered by a map tool capture like add feature.
`multiFrameScope`	Creates a new scope which contains variables and functions relating to a `QgsLayoutMultiFrame`.
`notificationScope`	Creates a new scope which contains variables and functions relating to provider notifications
`processingAlgorithmScope`	Creates a new scope which contains variables and functions relating to a processing `algorithm`, when used with the specified `parameters` and `context`.
`processingModelAlgorithmScope`	Creates a new scope which contains variables and functions relating to a processing `model` algorithm, when used with the specified `parameters` and `context`.
`projectScope`	Creates a new scope which contains variables and functions relating to a QGIS project.
`registerContextFunctions`	Registers all known core functions provided by QgsExpressionContextScope objects.
`removeGlobalVariable`	Remove a global context variable.
`removeProjectVariable`	Remove project context variable.
`setGlobalVariable`	Sets a global context variable.
`setGlobalVariables`	Sets all global context variables.
`setLayerVariable`	Sets a layer context variable.
`setLayerVariables`	Sets all layer context variables.
`setLayoutItemVariable`	Sets a layout `item` context variable, with the given `name` and `value`.
`setLayoutItemVariables`	Sets all layout item context variables for an `item`.
`setLayoutMultiFrameVariable`	Sets a layout multi `frame` context variable, with the given `name` and `value`.
`setLayoutMultiFrameVariables`	Sets all layout multiframe context variables for an `frame`.
`setLayoutVariable`	Sets a layout context variable.
`setLayoutVariables`	Sets all layout context variables.
`setProjectVariable`	Sets a project context variable.
`setProjectVariables`	Sets all project context variables.
`updateSymbolScope`	Updates a symbol scope related to a QgsSymbol to an expression context.

Signals

Attributes

atlasScope(atlas: QgsLayoutAtlas) → QgsExpressionContextScope¶

Creates a new scope which contains variables and functions relating to a QgsLayoutAtlas. For instance, current page name and number.

Parameters: atlas – source atlas. If None, a set of default atlas variables will be added to the scope.

createFeatureBasedContext(feature: QgsFeature, fields: QgsFields) → QgsExpressionContext¶: Helper function for creating an expression context which contains just a feature and fields collection. Generally this method should not be used as the created context does not include standard scopes such as the global and project scopes.

formScope(formFeature: QgsFeature = QgsFeature(), formMode: str = '') → QgsExpressionContextScope¶: Creates a new scope which contains functions and variables from the current attribute form/table feature. The variables and values in this scope will reflect the current state of the form/row being edited. The formMode (SingleEditMode etc.) is passed as text

New in version 3.2.

globalProjectLayerScopes(layer: QgsMapLayer) → List[QgsExpressionContextScope]¶: Creates a list of three scopes: global, layer’s project and layer.

New in version 3.0.

globalScope() → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to the global QGIS context. For instance, QGIS version numbers and variables specified through QGIS options.

See also

setGlobalVariable()

layerScope(layer: QgsMapLayer) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a QgsMapLayer. For instance, layer name, id and fields.

layoutItemScope(item: QgsLayoutItem) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a QgsLayoutItem. For instance, item size and position.

See also

setLayoutItemVariable()

See also

setLayoutItemVariables()

New in version 3.0.

layoutScope(layout: QgsLayout) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a QgsLayout layout. For instance, number of pages and page sizes.

New in version 3.0.

mapSettingsScope(mapSettings: QgsMapSettings) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a QgsMapSettings object. For instance, map scale and rotation.

mapToolCaptureScope(matches: Iterable[QgsPointLocator.Match]) → QgsExpressionContextScope¶: Sets the expression context variables which are available for expressions triggered by a map tool capture like add feature.

New in version 3.0.

multiFrameScope(frame: QgsLayoutMultiFrame) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a QgsLayoutMultiFrame.

See also

setLayoutMultiFrameVariable()

See also

setLayoutMultiFrameVariables()

New in version 3.10.

notificationScope(message: str = '') → QgsExpressionContextScope¶

Creates a new scope which contains variables and functions relating to provider notifications

Parameters: message – the notification message

processingAlgorithmScope(algorithm: QgsProcessingAlgorithm, parameters: Dict[str, Any], context: QgsProcessingContext) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a processing algorithm, when used with the specified parameters and context. For instance, algorithm name and parameter functions.

See also

processingModelAlgorithmScope()

processingModelAlgorithmScope(model: QgsProcessingModelAlgorithm, parameters: Dict[str, Any], context: QgsProcessingContext) → QgsExpressionContextScope¶: Creates a new scope which contains variables and functions relating to a processing model algorithm, when used with the specified parameters and context. For instance, model name and path variables.

New in version 3.6.

projectScope(project: QgsProject) → QgsExpressionContextScope¶

Creates a new scope which contains variables and functions relating to a QGIS project. For instance, project path and title, and variables specified through the project properties.

Parameters: project – What project to use

See also

setProjectVariable()

registerContextFunctions()¶: Registers all known core functions provided by QgsExpressionContextScope objects.

removeGlobalVariable(name: str)¶

Remove a global context variable.

Parameters: name – variable name

See also

setGlobalVariable()

See also

setGlobalVariables()

See also

globalScope()

removeProjectVariable(project: QgsProject, name: str)¶

Remove project context variable.

Parameters

project – Project to apply changes to
name – variable name

See also

setProjectVariable()

See also

setProjectVariables()

See also

projectScope()

setGlobalVariable(name: str, value: Any)¶

Sets a global context variable. This variable will be contained within scopes retrieved via globalScope().

Parameters

name – variable name
value – variable value

See also

setGlobalVariable()

See also

globalScope()

See also

removeGlobalVariable()

setGlobalVariables(variables: Dict[str, Any])¶

Sets all global context variables. Existing global variables will be removed and replaced with the variables specified.

Parameters: variables – new set of global variables

See also

setGlobalVariable()

See also

globalScope()

See also

removeGlobalVariable()

setLayerVariable(layer: QgsMapLayer, name: str, value: Any)¶

Sets a layer context variable. This variable will be contained within scopes retrieved via layerScope().

Parameters

layer – map layer
name – variable name
value – variable value

See also

setLayerVariables()

See also

layerScope()

setLayerVariables(layer: QgsMapLayer, variables: Dict[str, Any])¶

Sets all layer context variables. Existing layer variables will be removed and replaced with the variables specified.

Parameters

layer – map layer
variables – new set of layer variables

See also

setLayerVariable()

See also

layerScope()

setLayoutItemVariable(item: QgsLayoutItem, name: str, value: Any)¶: Sets a layout item context variable, with the given name and value. This variable will be contained within scopes retrieved via layoutItemScope().

See also

setLayoutItemVariables()

See also

layoutItemScope()

New in version 3.0.

setLayoutItemVariables(item: QgsLayoutItem, variables: Dict[str, Any])¶: Sets all layout item context variables for an item. Existing variables will be removed and replaced with the variables specified.

See also

setLayoutItemVariable()

See also

layoutItemScope()

New in version 3.0.

setLayoutMultiFrameVariable(frame: QgsLayoutMultiFrame, name: str, value: Any)¶: Sets a layout multi frame context variable, with the given name and value. This variable will be contained within scopes retrieved via multiFrameScope().

See also

setLayoutItemVariables()

See also

multiFrameScope()

New in version 3.10.

setLayoutMultiFrameVariables(frame: QgsLayoutMultiFrame, variables: Dict[str, Any])¶: Sets all layout multiframe context variables for an frame. Existing variables will be removed and replaced with the variables specified.

See also

setLayoutMultiFrameVariable()

See also

multiFrameScope()

New in version 3.10.