Class: QgsProcessingContext¶

class qgis.core.QgsProcessingContext¶

Bases: sip.wrapper

Constructor for QgsProcessingContext.

Contains information about the context in which a processing algorithm is executed.

Contextual information includes settings such as the associated project, and expression context.

New in version 3.0: Enums

Methods

`addLayerToLoadOnCompletion`	Adds a `layer` to load (by ID or datasource) into the canvas upon completion of the algorithm or model.
`copyThreadSafeSettings`	Copies all settings which are safe for use across different threads from `other` to this context.
`defaultEncoding`	Returns the default encoding to use for newly created files.
`expressionContext`	Returns the expression context.
`feedback`	Returns the associated feedback object.
`flags`	Returns any flags set in the context.
`getMapLayer`	Returns a map layer from the context with a matching `identifier`.
`invalidGeometryCheck`	Returns the behavior used for checking invalid geometries in input layers.
`layerToLoadOnCompletionDetails`	Returns a reference to the details for a given `layer` which is loaded on completion of the algorithm or model.
`layersToLoadOnCompletion`	Returns a map of layers (by ID or datasource) to LayerDetails, to load into the canvas upon completion of the algorithm or model.
`project`	Returns the project in which the algorithm is being executed.
`pushToThread`	Pushes the thread affinity for the context (including all layers contained in the temporaryLayerStore()) into another `thread`.
`setDefaultEncoding`	Sets the default `encoding` to use for newly created files.
`setExpressionContext`	Sets the expression `context`.
`setFeedback`	Sets an associated `feedback` object.
`setFlags`	Sets `flags` for the context.
`setInvalidGeometryCallback`	Sets a callback function to use when encountering an invalid geometry and invalidGeometryCheck() is set to GeometryAbortOnInvalid.
`setInvalidGeometryCheck`	Sets the behavior used for checking invalid geometries in input layers.
`setLayersToLoadOnCompletion`	Sets the map of `layers` (by ID or datasource) to LayerDetails, to load into the canvas upon completion of the algorithm or model.
`setProject`	Sets the `project` in which the algorithm will be executed.
`setTransformContext`	Sets the coordinate transform `context`.
`setTransformErrorCallback`	Sets a callback function to use when encountering a transform error when iterating features.
`takeResultLayer`	Takes the result map layer with matching `id` from the context and transfers ownership of it back to the caller.
`takeResultsFrom`	Takes the results from another `context` and merges them with the results currently stored in this context.
`temporaryLayerStore`	Returns a reference to the layer store used for storing temporary layers during algorithm execution.
`thread`	Returns the thread in which the context lives.
`transformContext`	Returns the coordinate transform context.
`willLoadLayerOnCompletion`	Returns true if the given `layer` (by ID or datasource) will be loaded into the current project upon completion of the algorithm or model.

Signals

Attributes

class Flag¶: Bases: int

class Flags¶

Bases: sip.wrapper

QgsProcessingContext.Flags(Union[QgsProcessingContext.Flags, QgsProcessingContext.Flag]) QgsProcessingContext.Flags(QgsProcessingContext.Flags)

class LayerDetails(name: str, project: QgsProject, outputName: str = '', layerTypeHint: QgsProcessingUtils.LayerHint = QgsProcessingUtils.UnknownType)¶

Bases: sip.wrapper

Constructor for LayerDetails.

QgsProcessingContext.LayerDetails() Default constructor

QgsProcessingContext.LayerDetails(QgsProcessingContext.LayerDetails)

Details for layers to load into projects.

New in version 3.0.

layerTypeHint¶

name¶

outputName¶

postProcessor(self) → QgsProcessingLayerPostProcessorInterface¶: Layer post-processor. May be None if no post-processing is required.

See also

setPostProcessor()

New in version 3.2.

project¶

setPostProcessor(self, processor: QgsProcessingLayerPostProcessorInterface)¶

Sets the layer post-processor. May be None if no post-processing is required.

Ownership of processor is transferred.

See also

postProcessor()

New in version 3.2.

addLayerToLoadOnCompletion(self, layer: str, details: QgsProcessingContext.LayerDetails)¶: Adds a layer to load (by ID or datasource) into the canvas upon completion of the algorithm or model. The details parameter dictates the LayerDetails.

See also

setLayersToLoadOnCompletion()

See also

layersToLoadOnCompletion()

See also

willLoadLayerOnCompletion()

See also

layerToLoadOnCompletionDetails()

copyThreadSafeSettings(self, other: QgsProcessingContext)¶: Copies all settings which are safe for use across different threads from other to this context.

defaultEncoding(self) → str¶: Returns the default encoding to use for newly created files.

See also

setDefaultEncoding()

expressionContext(self) → QgsExpressionContext¶: Returns the expression context.

feedback(self) → QgsProcessingFeedback¶: Returns the associated feedback object.

See also

setFeedback()

flags(self) → QgsProcessingContext.Flags¶: Returns any flags set in the context.

See also

setFlags()

getMapLayer(self, identifier: str) → QgsMapLayer¶

Returns a map layer from the context with a matching identifier. This method considers layer IDs, names and sources when matching the identifier (see QgsProcessingUtils.mapLayerFromString() for details).

Ownership is not transferred and remains with the context.

See also

takeResultLayer()

invalidGeometryCheck(self) → QgsFeatureRequest.InvalidGeometryCheck¶: Returns the behavior used for checking invalid geometries in input layers.

See also

setInvalidGeometryCheck()

layerToLoadOnCompletionDetails(self, layer: str) → QgsProcessingContext.LayerDetails¶: Returns a reference to the details for a given layer which is loaded on completion of the algorithm or model.

Warning

First check willLoadLayerOnCompletion(), or calling this method will incorrectly add layer as a layer to load on completion.

See also

willLoadLayerOnCompletion()

See also

addLayerToLoadOnCompletion()

See also

setLayersToLoadOnCompletion()

See also

layersToLoadOnCompletion()

New in version 3.2.

layersToLoadOnCompletion(self) → object¶: Returns a map of layers (by ID or datasource) to LayerDetails, to load into the canvas upon completion of the algorithm or model.

See also

setLayersToLoadOnCompletion()

See also

addLayerToLoadOnCompletion()

See also

willLoadLayerOnCompletion()

See also

layerToLoadOnCompletionDetails()

project(self) → QgsProject¶: Returns the project in which the algorithm is being executed.

See also

setProject()

pushToThread(self, thread: QThread)¶: Pushes the thread affinity for the context (including all layers contained in the temporaryLayerStore()) into another thread. This method is only safe to call when the current thread matches the existing thread affinity for the context (see thread()).

See also

thread()

setDefaultEncoding(self, encoding: str)¶: Sets the default encoding to use for newly created files.

See also

defaultEncoding()

setExpressionContext(self, context: QgsExpressionContext)¶: Sets the expression context.

setFeedback(self, feedback: QgsProcessingFeedback)¶: Sets an associated feedback object. This allows context related functions to report feedback and errors to users and processing logs. While ideally this feedback object should outlive the context, only a weak pointer to feedback is stored and no errors will occur if feedback is deleted before the context. Ownership of feedback is not transferred.

See also

setFeedback()

setFlags(self, flags: Union[QgsProcessingContext.Flags, QgsProcessingContext.Flag])¶: Sets flags for the context.

See also

flags()

setInvalidGeometryCallback(self, Callable[..., None])¶: Sets a callback function to use when encountering an invalid geometry and invalidGeometryCheck() is set to GeometryAbortOnInvalid. This function will be called using the feature with invalid geometry as a parameter.

See also

invalidGeometryCallback()

New in version 3.0.

setInvalidGeometryCheck(self, check: QgsFeatureRequest.InvalidGeometryCheck)¶: Sets the behavior used for checking invalid geometries in input layers. Settings this to anything but QgsFeatureRequest.GeometryNoCheck will also reset the invalidGeometryCallback() to a default implementation.

See also

invalidGeometryCheck()

setLayersToLoadOnCompletion(self, layers: Dict[str, QgsProcessingContext.LayerDetails])¶: Sets the map of layers (by ID or datasource) to LayerDetails, to load into the canvas upon completion of the algorithm or model.

See also

addLayerToLoadOnCompletion()

See also

layersToLoadOnCompletion()

See also

willLoadLayerOnCompletion()

See also

layerToLoadOnCompletionDetails()

setProject(self, project: QgsProject)¶

Sets the project in which the algorithm will be executed.

This also automatically sets the transformContext() to match the project’s transform context.

See also

project()

setTransformContext(self, context: QgsCoordinateTransformContext)¶

Sets the coordinate transform context.

Note that setting a project for the context will automatically set the coordinate transform context.

See also

transformContext()

setTransformErrorCallback(self, Callable[..., None])¶: Sets a callback function to use when encountering a transform error when iterating features. This function will be called using the feature which encountered the transform error as a parameter.

See also

transformErrorCallback()

New in version 3.0.

takeResultLayer(self, id: str) → QgsMapLayer¶: Takes the result map layer with matching id from the context and transfers ownership of it back to the caller. This method can be used to remove temporary layers which are not required for further processing from a context.

See also

getMapLayer()

takeResultsFrom(self, context: QgsProcessingContext)¶: Takes the results from another context and merges them with the results currently stored in this context. This includes settings like any layers loaded in the temporaryLayerStore() and layersToLoadOnCompletion(). This is only safe to call when both this context and the other context share the same thread() affinity, and that thread is the current thread.

temporaryLayerStore(self) → QgsMapLayerStore¶: Returns a reference to the layer store used for storing temporary layers during algorithm execution.

thread(self) → QThread¶: Returns the thread in which the context lives.

See also

pushToThread()

transformContext(self) → QgsCoordinateTransformContext¶: Returns the coordinate transform context.

See also

setTransformContext()

willLoadLayerOnCompletion(self, layer: str) → bool¶: Returns true if the given layer (by ID or datasource) will be loaded into the current project upon completion of the algorithm or model.

See also

layersToLoadOnCompletion()

See also

setLayersToLoadOnCompletion()

See also

addLayerToLoadOnCompletion()

See also

layerToLoadOnCompletionDetails()

New in version 3.2.