Class: QgsProcessingContext¶

class qgis.core.QgsProcessingContext¶

Bases: sip.wrapper

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.

QgsProcessingContext() Constructor for QgsProcessingContext.

Enums

ProcessArgumentFlag

Bases: enum.IntEnum

Methods

addLayerToLoadOnCompletion

Adds a layer to load (by ID or datasource) into the canvas upon completion of the algorithm or model.

areaUnit

Returns the area unit to use for area calculations.

asQgisProcessArguments

Returns list of the equivalent qgis_process arguments representing the settings from the context.

copyThreadSafeSettings

Copies all settings which are safe for use across different threads from other to this context.

currentTimeRange

Returns the current time range to use for temporal operations.

defaultEncoding

Returns the default encoding to use for newly created files.

distanceUnit

Returns the distance unit to use for distance calculations.

ellipsoid

Returns the ellipsoid to use for distance and area calculations.

exportToMap

Exports the context's settings to a variant map.

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.

logLevel

Returns the logging level for algorithms to use when pushing feedback messages to users.

maximumThreads

Returns the (optional) number of threads to use when running algorithms.

preferredRasterFormat

Returns the preferred raster format to use for vector outputs.

preferredVectorFormat

Returns the preferred vector format to use for vector outputs.

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.

setAreaUnit

Sets the unit to use for area calculations.

setCurrentTimeRange

Sets the current time range to use for temporal operations.

setDefaultEncoding

Sets the default encoding to use for newly created files.

setDistanceUnit

Sets the unit to use for distance calculations.

setEllipsoid

Sets a specified ellipsoid to use for distance and area calculations.

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.

setLogLevel

Sets the logging level for algorithms to use when pushing feedback messages to users.

setMaximumThreads

Sets the (optional) number of threads to use when running algorithms.

setPreferredRasterFormat

Sets the preferred raster format to use for vector outputs.

setPreferredVectorFormat

Sets the preferred vector format to use for vector outputs.

setProject

Sets the project in which the algorithm will be executed.

setTemporaryFolder

Sets the (optional) temporary folder to use when running algorithms.

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.

temporaryFolder

Returns the (optional) temporary folder to use when running algorithms.

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.

Attributes

DefaultLevel

Unused

Verbose

DefaultLevel = 0¶

class Flag¶: Bases: int

class Flags¶
class Flags(Union[QgsProcessingContext.Flags, QgsProcessingContext.Flag])
class Flags(QgsProcessingContext.Flags): Bases: sip.wrapper

class LayerDetails¶

Bases: sip.wrapper

Details for layers to load into projects.

New in version 3.0.

QgsProcessingContext.LayerDetails(name: str, project: QgsProject, outputName: str = ‘’, layerTypeHint: QgsProcessingUtils.LayerHint = QgsProcessingUtils.LayerHint.UnknownType) Constructor for LayerDetails.

QgsProcessingContext.LayerDetails() Default constructor

QgsProcessingContext.LayerDetails(QgsProcessingContext.LayerDetails)

forceName¶

groupName¶

layerSortKey¶

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.

Return type:: QgsProcessingLayerPostProcessorInterface

project¶

setOutputLayerName(self, layer: QgsMapLayer)¶

Sets a layer name to match this output, respecting any local user settings which affect this name.

New in version 3.10.1.

Parameters:: layer (QgsMapLayer) –

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.

Parameters:: processor (QgsProcessingLayerPostProcessorInterface) –

class LogLevel¶: Bases: int

class ProcessArgumentFlag(value)¶

Bases: enum.IntEnum

Flags controlling the results given by asQgisProcessArguments().

New in version 3.24.

IncludeProjectPath: Include the associated project path argument

IncludeProjectPath = 1¶

class ProcessArgumentFlags¶
class ProcessArgumentFlags(Union[QgsProcessingContext.ProcessArgumentFlags, QgsProcessingContext.ProcessArgumentFlag])
class ProcessArgumentFlags(QgsProcessingContext.ProcessArgumentFlags): Bases: sip.wrapper

Unused = 1¶

Verbose = 1¶

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()

Parameters:

layer (str) –
details (QgsProcessingContext.LayerDetails) –

areaUnit(self) → Qgis.AreaUnit¶

Returns the area unit to use for area calculations.

See also

setAreaUnit()

See also

distanceUnit()

New in version 3.16.

Return type:: Qgis.AreaUnit

asQgisProcessArguments(self, flags: QgsProcessingContext.ProcessArgumentFlags | QgsProcessingContext.ProcessArgumentFlag = QgsProcessingContext.ProcessArgumentFlags()) → List[str]¶

Returns list of the equivalent qgis_process arguments representing the settings from the context.

New in version 3.24.

Parameters:: flags (Union[QgsProcessingContext.ProcessArgumentFlags) –
Return type:: List[str]

copyThreadSafeSettings(self, other: QgsProcessingContext)¶

Copies all settings which are safe for use across different threads from other to this context.

Parameters:: other (QgsProcessingContext) –

currentTimeRange(self) → QgsDateTimeRange¶

Returns the current time range to use for temporal operations.

See also

setCurrentTimeRange()

New in version 3.18.

Return type:: QgsDateTimeRange

defaultEncoding(self) → str¶

Returns the default encoding to use for newly created files.

See also

setDefaultEncoding()

Return type:: str

distanceUnit(self) → Qgis.DistanceUnit¶

Returns the distance unit to use for distance calculations.

See also

setDistanceUnit()

See also

areaUnit()

New in version 3.16.

Return type:: Qgis.DistanceUnit

ellipsoid(self) → str¶

Returns the ellipsoid to use for distance and area calculations.

See also

setEllipsoid()

New in version 3.16.

Return type:: str

exportToMap(self) → Dict[str, Any]¶

Exports the context’s settings to a variant map.

New in version 3.24.

Return type:: Dict[str, Any]

expressionContext(self) → QgsExpressionContext¶

Returns the expression context.

Return type:: QgsExpressionContext

feedback(self) → QgsProcessingFeedback¶

Returns the associated feedback object.

See also

setFeedback()

Return type:: QgsProcessingFeedback

flags(self) → QgsProcessingContext.Flags¶

Returns any flags set in the context.

See also

setFlags()

Return type:: QgsProcessingContext.Flags

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()

Parameters:: identifier (str) –
Return type:: QgsMapLayer

invalidGeometryCheck(self) → QgsFeatureRequest.InvalidGeometryCheck¶

Returns the behavior used for checking invalid geometries in input layers.

See also

setInvalidGeometryCheck()

Return type:: QgsFeatureRequest.InvalidGeometryCheck

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.

Parameters:: layer (str) –
Return type:: QgsProcessingContext.LayerDetails

layersToLoadOnCompletion(self) → Dict[str, QgsProcessingContext.LayerDetails]¶

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()

Return type:: Dict[str, QgsProcessingContext.LayerDetails]

logLevel(self) → QgsProcessingContext.LogLevel¶

Returns the logging level for algorithms to use when pushing feedback messages to users.

See also

setLogLevel()

New in version 3.20.

Return type:: QgsProcessingContext.LogLevel

maximumThreads(self) → int¶

Returns the (optional) number of threads to use when running algorithms.

Warning

Not all algorithms which support multithreaded execution will respect this setting, depending on the multi-threading framework in use. Multithreaded algorithms must check this value and adapt their thread handling accordingly – the setting will not be automatically applied.

See also

setMaximumThreads()

New in version 3.32.

Return type:: int

preferredRasterFormat(self) → str¶

Returns the preferred raster format to use for vector outputs.

This method returns a file extension to use when creating raster outputs (e.g. “tif”). Generally, it is preferable to use the extension associated with a particular parameter, which can be retrieved through QgsProcessingDestinationParameter.defaultFileExtension(). However, in some cases, a specific parameter may not be available to call this method on (e.g. for an algorithm which has only an output folder parameter and which creates multiple output layers in that folder). In this case, the format returned by this function should be used when creating these outputs.

It is the algorithm’s responsibility to check whether the returned format is acceptable for the algorithm, and to provide an appropriate fallback when the returned format is not usable.

See also

setPreferredRasterFormat()

See also

preferredVectorFormat()

New in version 3.10.

Return type:: str

preferredVectorFormat(self) → str¶

Returns the preferred vector format to use for vector outputs.

This method returns a file extension to use when creating vector outputs (e.g. “shp”). Generally, it is preferable to use the extension associated with a particular parameter, which can be retrieved through QgsProcessingDestinationParameter.defaultFileExtension(). However, in some cases, a specific parameter may not be available to call this method on (e.g. for an algorithm which has only an output folder parameter and which creates multiple output layers in that folder). In this case, the format returned by this function should be used when creating these outputs.

It is the algorithm’s responsibility to check whether the returned format is acceptable for the algorithm, and to provide an appropriate fallback when the returned format is not usable.

See also

setPreferredVectorFormat()

See also

preferredRasterFormat()

New in version 3.10.

Return type:: str

project(self) → QgsProject¶

Returns the project in which the algorithm is being executed.

See also

setProject()

Return type:: QgsProject

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()

Parameters:: thread (QThread) –

setAreaUnit(self, areaUnit: Qgis.AreaUnit)¶

Sets the unit to use for area calculations.

If not explicitly set, the unit will default to the project()’s area unit setting.

See also

areaUnit()

See also

setDistanceUnit()

New in version 3.16.

Parameters:: areaUnit (Qgis.AreaUnit) –

setCurrentTimeRange(self, currentTimeRange: QgsDateTimeRange)¶

Sets the current time range to use for temporal operations.

See also

currentTimeRange()

New in version 3.18.

Parameters:: currentTimeRange (QgsDateTimeRange) –

setDefaultEncoding(self, encoding: str)¶

Sets the default encoding to use for newly created files.

See also

defaultEncoding()

Parameters:: encoding (str) –

setDistanceUnit(self, unit: Qgis.DistanceUnit)¶

Sets the unit to use for distance calculations.

If not explicitly set, the unit will default to the project()’s distance unit setting.

See also

distanceUnit()

See also

setAreaUnit()

New in version 3.16.

Parameters:: unit (Qgis.DistanceUnit) –

setEllipsoid(self, ellipsoid: str)¶

Sets a specified ellipsoid to use for distance and area calculations.

If not explicitly set, the ellipsoid will default to the project()’s ellipsoid setting.

See also

ellipsoid()

New in version 3.16.

Parameters:: ellipsoid (str) –

setExpressionContext(self, context: QgsExpressionContext)¶

Sets the expression context.

Parameters:: context (QgsExpressionContext) –

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()

Parameters:: feedback (QgsProcessingFeedback) –

setFlags(self, flags: QgsProcessingContext.Flags | QgsProcessingContext.Flag)¶

Sets flags for the context.

See also

flags()

Parameters:: flags (Union[QgsProcessingContext.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()

Parameters:: check (QgsFeatureRequest.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()

Parameters:: layers (Dict[str) –

setLogLevel(self, level: QgsProcessingContext.LogLevel)¶

Sets the logging level for algorithms to use when pushing feedback messages to users.

See also

logLevel()

New in version 3.20.

Parameters:: level (QgsProcessingContext.LogLevel) –

setMaximumThreads(self, threads: int)¶

Sets the (optional) number of threads to use when running algorithms.

If set, this overrides the standard global Processing number of threads setting. Note that if algorithm implementation does not support multhreaded execution, this setting will be ignored.

Warning

Not all algorithms which support multithreaded execution will respect this setting, depending on the multi-threading framework in use. Multithreaded algorithms must check this value and adapt their thread handling accordingly – the setting will not be automatically applied.

See also

maximumThreads()

New in version 3.32.

Parameters:: threads (int) –

setPreferredRasterFormat(self, format: str)¶

Sets the preferred raster format to use for vector outputs.

This method sets a file extension to use when creating raster outputs (e.g. “tif”). Generally, it is preferable to use the extension associated with a particular parameter, which can be retrieved through QgsProcessingDestinationParameter.defaultFileExtension(). However, in some cases, a specific parameter may not be available to call this method on (e.g. for an algorithm which has only an output folder parameter and which creates multiple output layers in that folder). In this case, the format set by this function will be used when creating these outputs.

See also

preferredRasterFormat()

See also

setPreferredVectorFormat()

New in version 3.10.

Parameters:: format (str) –

setPreferredVectorFormat(self, format: str)¶

Sets the preferred vector format to use for vector outputs.

This method sets a file extension to use when creating vector outputs (e.g. “shp”). Generally, it is preferable to use the extension associated with a particular parameter, which can be retrieved through QgsProcessingDestinationParameter.defaultFileExtension(). However, in some cases, a specific parameter may not be available to call this method on (e.g. for an algorithm which has only an output folder parameter and which creates multiple output layers in that folder). In this case, the format set by this function will be used when creating these outputs.

See also

preferredVectorFormat()

See also

setPreferredRasterFormat()

New in version 3.10.

Parameters:: format (str) –

setProject(self, project: QgsProject)¶

Sets the project in which the algorithm will be executed.

This also automatically sets the transformContext(), ellipsoid(), distanceUnit() and areaUnit() to match the project’s settings.

See also

project()

Parameters:: project (QgsProject) –

setTemporaryFolder(self, folder: str)¶

Sets the (optional) temporary folder to use when running algorithms.

If set, this overrides the standard global Processing temporary folder and should be used for all temporary files created during algorithm execution.

See also

temporaryFolder()

New in version 3.32.

Parameters:: folder (str) –

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()

Parameters:: context (QgsCoordinateTransformContext) –

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()

Parameters:: id (str) –
Return type:: QgsMapLayer

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.