Class: QgsProcessingUtils¶
- class qgis.core.QgsProcessingUtils¶
Bases:
sip.wrapper
Utility functions for use with processing classes.
New in version 3.0:
Enums
Bases:
enum.IntEnum
Methods
Combines two field lists, avoiding duplicate field names (in a case-insensitive manner).
Combines the extent of several map
layers
.Returns a list of map layers from a
project
which are compatible with the processing framework.Returns a list of mesh layers from a
project
which are compatible with the processing framework.Returns a list of raster layers from a
project
which are compatible with the processing framework.Returns a list of vector layers from a
project
which are compatible with the processing framework.Converts a source vector
layer
to a file path of a vector layer of compatible format.Converts a source vector
layer
to a file path and layer name of a vector layer of compatible format.Creates a feature sink ready for adding features.
Decodes a provider key and layer
uri
from an encoded string, for use withencodeProviderKeyAndUri()
Returns the default raster extension to use, in the absence of all other constraints (e.g.
Returns the default vector extension to use, in the absence of all other constraints (e.g.
Encodes a provider key and layer
uri
to a single string, for use withdecodeProviderKeyAndUri()
Returns a list of field indices parsed from the given list of field names.
Returns a HTML formatted version of the help text encoded in a variant
map
for a specifiedalgorithm
.Converts an
input
parameter value for use in source iterating mode, where one individual sink is created per input feature.Returns a temporary filename for a given file, putting it into a temporary folder (creating that folder in the process), but not changing the
basename
.Returns a subset of fields based on the indices of desired fields.
Interprets a string as a map layer within the supplied
context
.Normalizes a layer
source
string for safe comparison across different operating system environments.Converts a string to a Python string literal.
Returns a session specific processing temporary folder for use in processing algorithms.
Converts a variant
value
to a coordinate reference system.Converts a variant to a Python literal.
Converts a variant
value
to a new feature source.- class LayerHint(value)¶
Bases:
enum.IntEnum
Layer type hints.
New in version 3.4.
UnknownType
: Unknown layer typeVector
: Vector layer typeRaster
: Raster layer typeMesh
: Mesh layer type, since QGIS 3.6
- combineFields(fieldsA: QgsFields, fieldsB: QgsFields, fieldsBPrefix: str = '') QgsFields ¶
Combines two field lists, avoiding duplicate field names (in a case-insensitive manner).
Duplicate field names will be altered to “name_2”, “name_3”, etc, finding the first non-duplicate name.
Note
Some output file formats (e.g. shapefiles) have restrictions on the maximum length of field names, so be aware that the results of calling this method may be truncated when saving to these formats.
- combineLayerExtents(layers: Iterable[QgsMapLayer], crs: QgsCoordinateReferenceSystem, context: QgsProcessingContext) QgsRectangle ¶
Combines the extent of several map
layers
. If specified, the targetcrs
will be used to transform the layer’s extent to the desired output reference system using the specifiedcontext
.New in version 3.8.
combineLayerExtents(layers: Iterable[QgsMapLayer], crs:
QgsCoordinateReferenceSystem
= QgsCoordinateReferenceSystem()) -> QgsRectangle Combines the extent of several maplayers
. If specified, the targetcrs
will be used to transform the layer’s extent to the desired output reference system.Deprecated since version Use: version with
QgsProcessingContext
argument instead- Parameters
layers (Iterable[QgsMapLayer]) –
crs (QgsCoordinateReferenceSystem) –
context (QgsProcessingContext) –
- Return type
- compatibleLayers(project: QgsProject, sort: bool = True) List[QgsMapLayer] ¶
Returns a list of map layers from a
project
which are compatible with the processing framework.If the
sort
argument isTrue
then the layers will be sorted by theirQgsMapLayer.name()
value.See also
See also
- Parameters
project (QgsProject) –
sort (bool = True) –
- Return type
List[QgsMapLayer]
- compatibleMeshLayers(project: QgsProject, sort: bool = True) List[QgsMeshLayer] ¶
Returns a list of mesh layers from a
project
which are compatible with the processing framework.If the
sort
argument isTrue
then the layers will be sorted by theirQgsMapLayer.name()
value.See also
See also
See also
New in version 3.6.
- Parameters
project (QgsProject) –
sort (bool = True) –
- Return type
List[QgsMeshLayer]
- compatibleRasterLayers(project: QgsProject, sort: bool = True) List[QgsRasterLayer] ¶
Returns a list of raster layers from a
project
which are compatible with the processing framework.If the
sort
argument isTrue
then the layers will be sorted by theirQgsMapLayer.name()
value.See also
See also
See also
- Parameters
project (QgsProject) –
sort (bool = True) –
- Return type
List[QgsRasterLayer]
- compatibleVectorLayers(project: QgsProject, sourceTypes: Iterable[int] = [], sort: bool = True) List[QgsVectorLayer] ¶
Returns a list of vector layers from a
project
which are compatible with the processing framework.The
sourceTypes
list should be filled with a list ofQgsProcessing
.SourceType values. If thesourceTypes
list is non-empty then the layers will be sorted so that only layers with the specified source type included in the list will be returned. Leaving thesourceTypes
list empty will cause all vector layers, regardless of their geometry type, to be returned.If the
sort
argument isTrue
then the layers will be sorted by theirQgsMapLayer.name()
value.See also
See also
See also
- Parameters
project (QgsProject) –
sourceTypes (Iterable[int] = []) –
sort (bool = True) –
- Return type
List[QgsVectorLayer]
- convertToCompatibleFormat(layer: QgsVectorLayer, selectedFeaturesOnly: bool, baseName: str, compatibleFormats: Iterable[str], preferredFormat: str, context: QgsProcessingContext, feedback: QgsProcessingFeedback, featureLimit: int = - 1) str ¶
Converts a source vector
layer
to a file path of a vector layer of compatible format.If the specified
layer
is not of the format listed in thecompatibleFormats
argument, then the layer will first be exported to a compatible format in a temporary location usingbaseName
. The function will then return the path to that temporary file.compatibleFormats
should consist entirely of lowercase file extensions, e.g. ‘shp’.The
preferredFormat
argument is used to specify to desired file extension to use when a temporary layer export is required. This defaults to shapefiles.The
featureLimit
argument can be used to specify a limit on the number of features read from the layer.When an algorithm is capable of handling multi-layer input files (such as Geopackage), it is preferable to use
convertToCompatibleFormatAndLayerName()
which may avoid conversion in more situations.- Parameters
layer (QgsVectorLayer) –
selectedFeaturesOnly (bool) –
baseName (str) –
compatibleFormats (Iterable[str]) –
preferredFormat (str) –
context (QgsProcessingContext) –
feedback (QgsProcessingFeedback) –
featureLimit (int = -1) –
- Return type
str
- convertToCompatibleFormatAndLayerName(layer: QgsVectorLayer, selectedFeaturesOnly: bool, baseName: str, compatibleFormats: Iterable[str], preferredFormat: str, context: QgsProcessingContext, feedback: QgsProcessingFeedback, featureLimit: int = - 1) Tuple[str, str] ¶
Converts a source vector
layer
to a file path and layer name of a vector layer of compatible format.If the specified
layer
is not of the format listed in thecompatibleFormats
argument, then the layer will first be exported to a compatible format in a temporary location usingbaseName
. The function will then return the path to that temporary file.compatibleFormats
should consist entirely of lowercase file extensions, e.g. ‘shp’.The
featureLimit
argument can be used to specify a limit on the number of features read from the layer.The
preferredFormat
argument is used to specify to desired file extension to use when a temporary layer export is required. This defaults to shapefiles.This method should be preferred over
convertToCompatibleFormat()
when an algorithm is able to correctly handle files with multiple layers. UnlikeconvertToCompatibleFormat()
, it will not force a conversion in this case and will return the target layer name in thelayerName
argument.- Parameters
layer (QgsVectorLayer) – source layer to convert (if required)
selectedFeaturesOnly (bool) –
True
if only selected features from the layer should be usedbaseName (str) – base file name for converted layer, if required
compatibleFormats (Iterable[str]) – a list of lowercase file extensions compatible with the algorithm
preferredFormat (str) – preferred format extension to use if conversion if required
context (QgsProcessingContext) – processing context
feedback (QgsProcessingFeedback) – feedback object
featureLimit (int = -1) – can be used to place a limit on the maximum number of features read from the layer
- Return type
Tuple[str, str]
- Returns
path to source layer, or nearly converted compatible layer
layerName: will be set to the target layer name for multi-layer sources (e.g. Geopackage)
See also
New in version 3.10.
- createFeatureSink(destination: str, context: QgsProcessingContext, fields: QgsFields, geometryType: QgsWkbTypes.Type, crs: QgsCoordinateReferenceSystem, createOptions: Dict[str, Any] = {}) Tuple[QgsFeatureSink, str] ¶
Creates a feature sink ready for adding features. The
destination
specifies a destination URI for the resultant layer. It may be updated in place to reflect the actual destination for the layer.Sink parameters such as desired
fields
,geometryType
andcrs
must be specified.The
createOptions
map can be used to specify additional sink creation options, which are passed to the underlying provider when creating new layers. Known options also include ‘fileEncoding’, which is used to specify a file encoding to use for created files. If ‘fileEncoding’ is not specified, the default encoding from thecontext
will be used.If a layer is created for the feature sink, the layer will automatically be added to the
context
’s temporary layer store.Note
this version of the
createFeatureSink()
function has an API designed around use from the SIP bindings. c++ code should call the othercreateFeatureSink()
version.Note
available in Python bindings as
createFeatureSink()
- Parameters
destination (str) –
context (QgsProcessingContext) –
fields (QgsFields) –
geometryType (QgsWkbTypes.Type) –
crs (QgsCoordinateReferenceSystem) –
createOptions (Dict[str) –
- Return type
Tuple[
QgsFeatureSink
, str]
- decodeProviderKeyAndUri(string: str) Tuple[bool, str, str] ¶
Decodes a provider key and layer
uri
from an encoded string, for use withencodeProviderKeyAndUri()
- Parameters
string (str) – encoded string, as returned by
encodeProviderKeyAndUri()
- Return type
Tuple[bool, str, str]
- Returns
True
ifstring
was successfully decodedproviderKey: ID key for corresponding data provider
uri: decoded layer uri
New in version 3.14.
- defaultRasterExtension() str ¶
Returns the default raster extension to use, in the absence of all other constraints (e.g. provider based support for extensions).
This method returns the user-set default extension from the processing settings, or a fallback value of “tif”.
See also
New in version 3.10.
- Return type
str
- defaultVectorExtension() str ¶
Returns the default vector extension to use, in the absence of all other constraints (e.g. provider based support for extensions).
This method returns the user-set default extension from the processing settings, or a fallback value of “gpkg”.
See also
New in version 3.10.
- Return type
str
- encodeProviderKeyAndUri(providerKey: str, uri: str) str ¶
Encodes a provider key and layer
uri
to a single string, for use withdecodeProviderKeyAndUri()
New in version 3.14.
- Parameters
providerKey (str) –
uri (str) –
- Return type
str
- fieldNamesToIndices(fieldNames: Iterable[str], fields: QgsFields) List[int] ¶
Returns a list of field indices parsed from the given list of field names. Unknown field names are ignored. If the list of field names is empty, it is assumed that all fields are required.
New in version 3.2.
- Parameters
fieldNames (Iterable[str]) –
fields (QgsFields) –
- Return type
List[int]
- formatHelpMapAsHtml(map: Dict[str, Any], algorithm: QgsProcessingAlgorithm) str ¶
Returns a HTML formatted version of the help text encoded in a variant
map
for a specifiedalgorithm
.- Parameters
map (Dict[str) –
algorithm (QgsProcessingAlgorithm) –
- Return type
str
- generateIteratingDestination(input: Any, id: Any, context: QgsProcessingContext) Any ¶
Converts an
input
parameter value for use in source iterating mode, where one individual sink is created per input feature. Theid
parameter represents the unique ID for this output, which is embedded into the resulting parameter value.- Parameters
input (Any) –
id (Any) –
context (QgsProcessingContext) –
- Return type
Any
- generateTempFilename(basename: str) str ¶
Returns a temporary filename for a given file, putting it into a temporary folder (creating that folder in the process), but not changing the
basename
.See also
- Parameters
basename (str) –
- Return type
str
- indicesToFields(indices: Iterable[int], fields: QgsFields) QgsFields ¶
Returns a subset of fields based on the indices of desired fields.
New in version 3.2.
- mapLayerFromString(string: str, context: QgsProcessingContext, allowLoadingNewLayers: bool = True, typeHint: QgsProcessingUtils.LayerHint = QgsProcessingUtils.LayerHint.UnknownType) QgsMapLayer ¶
Interprets a string as a map layer within the supplied
context
.The method will attempt to load a layer matching the passed
string
. E.g. if the string matches a layer ID or name within the context’s project or temporary layer store then this layer will be returned. If the string is a file path andallowLoadingNewLayers
isTrue
, then the layer at this file path will be loaded and added to the context’s temporary layer store. Ownership of the layer remains with thecontext
or the context’s current project.The
typeHint
can be used to dictate the type of map layer expected.- Parameters
string (str) –
context (QgsProcessingContext) –
allowLoadingNewLayers (bool = True) –
typeHint (QgsProcessingUtils.LayerHint = QgsProcessingUtils.LayerHint.UnknownType) –
- Return type
- normalizeLayerSource(source: str) str ¶
Normalizes a layer
source
string for safe comparison across different operating system environments.- Parameters
source (str) –
- Return type
str
- stringToPythonLiteral(string: str) str ¶
Converts a string to a Python string literal. E.g. by replacing ‘ with '.
See also
- Parameters
string (str) –
- Return type
str
- tempFolder() str ¶
Returns a session specific processing temporary folder for use in processing algorithms.
See also
- Return type
str
- variantToCrs(value: Any, context: QgsProcessingContext, fallbackValue: Any = None) QgsCoordinateReferenceSystem ¶
Converts a variant
value
to a coordinate reference system.The optional
fallbackValue
can be used to specify a “default” value which is used ifvalue
cannot be successfully converted to a CRS.New in version 3.12.
- Parameters
value (Any) –
context (QgsProcessingContext) –
fallbackValue (Any = None) –
- Return type
- variantToPythonLiteral(value: Any) str ¶
Converts a variant to a Python literal.
See also
New in version 3.6.
- Parameters
value (Any) –
- Return type
str
- variantToSource(value: Any, context: QgsProcessingContext, fallbackValue: Any = None) QgsProcessingFeatureSource ¶
Converts a variant
value
to a new feature source.Sources will either be taken from
context
’s active project, or loaded from external sources and stored temporarily in thecontext
.The optional
fallbackValue
can be used to specify a “default” value which is used ifvalue
cannot be successfully converted to a source.This function creates a new object and the caller takes responsibility for deleting the returned object.
- Parameters
value (Any) –
context (QgsProcessingContext) –
fallbackValue (Any = None) –
- Return type