Class: 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.

Enums

LogLevel	alias of ProcessingLogLevel
ProcessArgumentFlag	Flags controlling the results given by asQgisProcessArguments().

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.
clearModelResult	Clears model results previously populated when the context was used to run a model algorithm.
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.
modelResult	Returns the model results, populated when the context is used to run a model algorithm.
preferredRasterFormat	Returns the preferred raster format to use for raster 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 raster 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

Unused

class qgis.core.QgsProcessingContext

Bases: object

class Flag

Bases: int

class Flags

class Flags(f: QgsProcessingContext.Flags | QgsProcessingContext.Flag)

class Flags(a0: QgsProcessingContext.Flags)

Bases: object

class LayerDetails

Bases: object

Details for layers to load into projects.

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

QgsProcessingContext.LayerDetails()

QgsProcessingContext.LayerDetails(a0: QgsProcessingContext.LayerDetails)

forceName: bool

Set to True if LayerDetails.name should always be used as the loaded layer name, regardless of the user’s local Processing settings.

Added in version 3.16.

groupName: str

Optional name for a layer tree group under which to place the layer when loading it into a project.

Added in version 3.32.

layerSortKey: int

Optional sorting key for sorting output layers when loading them into a project.

Layers with a greater sort key will be placed over layers with a lesser sort key.

Added in version 3.32.

layerTypeHint: LayerHint

Layer type hint.

Added in version 3.4.

name: str

Friendly name for layer, possibly for use when loading layer into project.

Warning

Instead of directly using this value, prefer to call setOutputLayerName() to generate a layer name which respects the user’s local Processing settings.

outputName: str

Associated output name from algorithm which generated the layer.

postProcessor(self) → QgsProcessingLayerPostProcessorInterface | None

Layer post-processor. May be None if no post-processing is required.

See also

setPostProcessor()

Added in version 3.2.

Return type:

Optional[QgsProcessingLayerPostProcessorInterface]

project: QgsProject

Destination project

setOutputLayerName(self, layer: QgsMapLayer | None)

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

Added in version 3.10.1.

Parameters:

layer (Optional[QgsMapLayer])

setPostProcessor(self, processor: QgsProcessingLayerPostProcessorInterface | None)

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

Ownership of processor is transferred.

See also

postProcessor()

Added in version 3.2.

Parameters:

processor (Optional[QgsProcessingLayerPostProcessorInterface])

LogLevel

alias of ProcessingLogLevel

class ProcessArgumentFlag(*values)

Bases: IntEnum

Flags controlling the results given by asQgisProcessArguments().

Added in version 3.24.

• IncludeProjectPath: Include the associated project path argument

IncludeProjectPath = 1

class ProcessArgumentFlags

class ProcessArgumentFlags(f: QgsProcessingContext.ProcessArgumentFlags | QgsProcessingContext.ProcessArgumentFlag)

class ProcessArgumentFlags(a0: QgsProcessingContext.ProcessArgumentFlags)

Bases: object

Unused = 1

addLayerToLoadOnCompletion(self, layer: str | None, 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 (Optional[str])

• details (QgsProcessingContext.LayerDetails)

areaUnit(self) → Qgis.AreaUnit

Returns the area unit to use for area calculations.

See also

setAreaUnit()

See also

distanceUnit()

Added 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.

Added in version 3.24.

Parameters:

flags (Union[QgsProcessingContext.ProcessArgumentFlags, QgsProcessingContext.ProcessArgumentFlag] = QgsProcessingContext.ProcessArgumentFlags())

Return type:

List[str]

clearModelResult(self)

Clears model results previously populated when the context was used to run a model algorithm.

Added in version 3.42.

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()

Added 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()

Added in version 3.16.

Return type:

Qgis.DistanceUnit

ellipsoid(self) → str

Returns the ellipsoid to use for distance and area calculations.

See also

setEllipsoid()

Added in version 3.16.

Return type:

str

exportToMap(self) → Dict[str, Any]

Exports the context’s settings to a variant map.

Added in version 3.24.

Return type:

Dict[str, Any]

expressionContext(self) → QgsExpressionContext

Returns the expression context.

Return type:

QgsExpressionContext

feedback(self) → QgsProcessingFeedback | None

Returns the associated feedback object.

See also

setFeedback()

Return type:

Optional[QgsProcessingFeedback]

flags(self) → QgsProcessingContext.Flags

Returns any flags set in the context.

See also

setFlags()

Return type:

QgsProcessingContext.Flags

getMapLayer(self, identifier: str | None) → QgsMapLayer | None

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 (Optional[str])

Return type:

Optional[QgsMapLayer]

invalidGeometryCheck(self) → Qgis.InvalidGeometryCheck

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

See also

setInvalidGeometryCheck()

Return type:

Qgis.InvalidGeometryCheck

layerToLoadOnCompletionDetails(self, layer: str | None) → 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()

Added in version 3.2.

Parameters:

layer (Optional[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) → Qgis.ProcessingLogLevel

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

See also

setLogLevel()

Added in version 3.20.

Return type:

Qgis.ProcessingLogLevel

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()

Added in version 3.32.

Return type:

int

modelResult(self) → QgsProcessingModelResult

Returns the model results, populated when the context is used to run a model algorithm.

Added in version 3.38.

Return type:

QgsProcessingModelResult

preferredRasterFormat(self) → str

Returns the preferred raster format to use for raster 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()

Added 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()

Added in version 3.10.

Return type:

str

project(self) → QgsProject | None

Returns the project in which the algorithm is being executed.

See also

setProject()

Return type:

Optional[QgsProject]

pushToThread(self, thread: QThread | None)

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 (Optional[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()

Added 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()

Added in version 3.18.

Parameters:

currentTimeRange (QgsDateTimeRange)

setDefaultEncoding(self, encoding: str | None)

Sets the default encoding to use for newly created files.

See also

defaultEncoding()

Parameters:

encoding (Optional[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()

Added in version 3.16.

Parameters:

unit (Qgis.DistanceUnit)

setEllipsoid(self, ellipsoid: str | None)

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()

Added in version 3.16.

Parameters:

ellipsoid (Optional[str])

setExpressionContext(self, context: QgsExpressionContext)

Sets the expression context.

Parameters:

context (QgsExpressionContext)

setFeedback(self, feedback: QgsProcessingFeedback | None)

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 (Optional[QgsProcessingFeedback])

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

Sets flags for the context.

See also

flags()

Parameters:

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

setInvalidGeometryCallback(self, a0: Callable[..., None] | 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()

Parameters:

a0 (Optional[Callable[..., None]])

setInvalidGeometryCheck(self, check: Qgis.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 (Qgis.InvalidGeometryCheck)

setLayersToLoadOnCompletion(self, layers: Dict[str | None, 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[Optional[str], QgsProcessingContext.LayerDetails])

setLogLevel(self, level: Qgis.ProcessingLogLevel)

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

See also

logLevel()

Added in version 3.20.

Parameters:

level (Qgis.ProcessingLogLevel)

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()

Added in version 3.32.

Parameters:

threads (int)

setPreferredRasterFormat(self, format: str | None)

Sets the preferred raster format to use for raster 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()

Added in version 3.10.

Parameters:

format (Optional[str])

setPreferredVectorFormat(self, format: str | None)

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()

Added in version 3.10.

Parameters:

format (Optional[str])

setProject(self, project: QgsProject | None)

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 (Optional[QgsProject])

setTemporaryFolder(self, folder: str | None)

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()

Added in version 3.32.

Parameters:

folder (Optional[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, a0: Callable[..., None] | 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()

Parameters:

a0 (Optional[Callable[..., None]])

takeResultLayer(self, id: str | None) → QgsMapLayer | None

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 (Optional[str])

Return type:

Optional[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.

Parameters:

context (QgsProcessingContext)

temporaryFolder(self) → str

Returns 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

setTemporaryFolder()

Added in version 3.32.

Return type:

str

temporaryLayerStore(self) → QgsMapLayerStore | None

Returns a reference to the layer store used for storing temporary layers during algorithm execution.

Return type:

Optional[QgsMapLayerStore]

thread(self) → QThread | None

Returns the thread in which the context lives.

See also

pushToThread()

Return type:

Optional[QThread]

transformContext(self) → QgsCoordinateTransformContext

Returns the coordinate transform context.

See also

setTransformContext()

Return type:

QgsCoordinateTransformContext

willLoadLayerOnCompletion(self, layer: str | None) → 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()

Added in version 3.2.

Parameters:

layer (Optional[str])

Return type:

bool