Class: QgsVectorLayerUtils

class qgis.core.QgsVectorLayerUtils

Bases: sip.wrapper

Contains utility methods for working with QgsVectorLayers.

New in version 3.0: Enums

Methods

createFeature

Creates a new feature ready for insertion into a layer.

createUniqueValue

Returns a new attribute value for the specified field index which is guaranteed to be unique.

duplicateFeature

Duplicates a feature and it’s children (one level deep).

getDoubleValues

Fetches all double values from a specified field name or expression.

getValues

Fetches all values from a specified field name or expression.

getValuesIterator

Create a feature iterator for a specified field name or expression.

makeFeatureCompatible

Converts input feature to be compatible with the given layer.

makeFeaturesCompatible

Converts input features to be compatible with the given layer.

matchAttributesToFields

Matches the attributes in feature to the specified fields.

validateAttribute

Tests an attribute value to check whether it passes all constraints which are present on the corresponding field.

valueExists

Returns true if the specified value already exists within a field.

Signals

Attributes

class QgsDuplicateFeatureContext

Bases: sip.wrapper

Constructor for QgsDuplicateFeatureContext

QgsVectorLayerUtils.QgsDuplicateFeatureContext(QgsVectorLayerUtils.QgsDuplicateFeatureContext)

Contains mainly the QMap with QgsVectorLayer and QgsFeatureIds do list all the duplicated features

New in version 3.0.

duplicatedFeatures(self, layer: QgsVectorLayer) → object

Returns the duplicated features in the given layer

New in version 3.0.

layers(self) → List[QgsVectorLayer]

Returns all the layers on which features have been duplicated

New in version 3.0.

createFeature(layer: QgsVectorLayer, geometry: QgsGeometry = QgsGeometry(), attributes: Dict[int, Any] = {}, context: QgsExpressionContext = None) → QgsFeature

Creates a new feature ready for insertion into a layer. Default values and constraints (e.g., unique constraints) will automatically be handled. An optional attribute map can be passed for the new feature to copy as many attribute values as possible from the map, assuming that they respect the layer’s constraints. Note that the created feature is not automatically inserted into the layer.

createUniqueValue(layer: QgsVectorLayer, fieldIndex: int, seed: Any = None) → Any

Returns a new attribute value for the specified field index which is guaranteed to be unique. The optional seed value can be used as a basis for generated values.

See also

valueExists()

duplicateFeature(layer: QgsVectorLayer, feature: QgsFeature, project: QgsProject, depth: int) → Tuple[QgsFeature, QgsVectorLayerUtils.QgsDuplicateFeatureContext]

Duplicates a feature and it’s children (one level deep). It calls CreateFeature, so default values and constraints (e.g., unique constraints) will automatically be handled. The duplicated feature will be automatically inserted into the layer. depth the higher this number the deeper the level - With depth > 0 the children of the feature are not duplicated duplicateFeatureContext stores all the layers and the featureids of the duplicated features (incl. children)

New in version 3.0.

getDoubleValues(layer: QgsVectorLayer, fieldOrExpression: str, selectedOnly: bool = False, feedback: QgsFeedback = None) → Tuple[List[float], bool, int]

Fetches all double values from a specified field name or expression. Null values or invalid expression results are skipped.

Parameters
  • layer – vector layer to retrieve values from

  • fieldOrExpression – field name or an expression string evaluating to a double value

  • ok – will be set to false if field or expression is invalid, otherwise true

  • selectedOnly – set to true to get values from selected features only

  • nullCount – optional pointer to integer to store number of null values encountered in

  • feedback – optional feedback object to allow cancellation

Returns

list of fetched values

See also

getValues()

New in version 3.0.

getValues(layer: QgsVectorLayer, fieldOrExpression: str, selectedOnly: bool = False, feedback: QgsFeedback = None) → Tuple[List[Any], bool]

Fetches all values from a specified field name or expression.

Parameters
  • layer – vector layer to retrieve values from

  • fieldOrExpression – field name or an expression string

  • ok – will be set to false if field or expression is invalid, otherwise true

  • selectedOnly – set to true to get values from selected features only

  • feedback – optional feedback object to allow cancellation

Returns

list of fetched values

New in version 3.0.

getValuesIterator(layer: QgsVectorLayer, fieldOrExpression: str, selectedOnly: bool) → Tuple[QgsFeatureIterator, bool]

Create a feature iterator for a specified field name or expression.

Parameters
  • layer – vector layer to retrieve values from

  • fieldOrExpression – field name or an expression string

  • ok – will be set to false if field or expression is invalid, otherwise true

  • selectedOnly – set to true to get values from selected features only

Returns

feature iterator

New in version 3.0.

makeFeatureCompatible(feature: QgsFeature, layer: QgsVectorLayer) → object

Converts input feature to be compatible with the given layer.

This function returns a new list of transformed features compatible with the input layer, note that the number of features returned might be greater than one when converting a multi part geometry to single part

The following operations will be performed to convert the input features: - convert single geometries to multi part - drop additional attributes - drop geometry if layer is geometry-less - add missing attribute fields - add back M/Z values (initialized to 0) - drop Z/M - convert multi part geometries to single part

New in version 3.4.

makeFeaturesCompatible(features: object, layer: QgsVectorLayer) → object

Converts input features to be compatible with the given layer.

This function returns a new list of transformed features compatible with the input layer, note that the number of features returned might be greater than the number of input features.

The following operations will be performed to convert the input features: - convert single geometries to multi part - drop additional attributes - drop geometry if layer is geometry-less - add missing attribute fields - add back M/Z values (initialized to 0) - drop Z/M - convert multi part geometries to single part

New in version 3.4.

matchAttributesToFields(feature: QgsFeature, fields: QgsFields)

Matches the attributes in feature to the specified fields.

This causes the attributes contained within the given feature to be rearranged (or in some cases dropped) in order to match the fields and order indicated by fields.

The exact behavior depends on whether or not feature has a valid fields container set (see QgsFeature.fields()). If a fields container is set, then the names of the feature’s fields are matched to fields. In this case attributes from feature will be rearranged or dropped in order to match the field names from fields.

If the feature does not have a valid fields container set, then the feature’s attributes are simply truncated to match the number of fields present in fields (or if less attributes are present in feature than in fields, the feature’s attributes are padded with NULL values to match the required length).

New in version 3.4.

validateAttribute(layer: QgsVectorLayer, feature: QgsFeature, attributeIndex: int, strength: QgsFieldConstraints.ConstraintStrength = QgsFieldConstraints.ConstraintStrengthNotSet, origin: QgsFieldConstraints.ConstraintOrigin = QgsFieldConstraints.ConstraintOriginNotSet) → Tuple[bool, List[str]]

Tests an attribute value to check whether it passes all constraints which are present on the corresponding field. Returns true if the attribute value is valid for the field. Any constraint failures will be reported in the errors argument. If the strength or origin parameter is set then only constraints with a matching strength/origin will be checked.

valueExists(layer: QgsVectorLayer, fieldIndex: int, value: Any, ignoreIds: object = QgsFeatureIds()) → bool

Returns true if the specified value already exists within a field. This method can be used to test for uniqueness of values inside a layer’s attributes. An optional list of ignored feature IDs can be provided, if so, any features with IDs within this list are ignored when testing for existence of the value.