Class: QgsGenericNumericTransformer¶

QgsPropertyTransformer subclass for scaling an input numeric value into an output numeric value.

Class Hierarchy¶

Base classes¶

QgsPropertyTransformer

Abstract base class for objects which transform the calculated value of a property. Possible uses include transformers which map a value into a scaled size or color from a gradient.

Methods

`exponent`	Returns the exponent for an exponential expression.
`maxOutputValue`	Returns the maximum calculated size.
`minOutputValue`	Returns the minimum calculated size.
`nullOutputValue`	Returns the size value when an expression evaluates to NULL.
`setExponent`	Sets the exponent for an exponential expression.
`setMaxOutputValue`	Sets the maximum calculated size.
`setMinOutputValue`	Sets the minimum calculated size.
`setNullOutputValue`	Sets the size value for when an expression evaluates to NULL.
`value`	Calculates the size corresponding to a specific input value.

Static Methods

fromExpression

Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.

class qgis.core.QgsGenericNumericTransformer[source]¶

Bases: QgsPropertyTransformer

__init__(minValue: float = 0, maxValue: float = 1, minOutput: float = 0, maxOutput: float = 1, nullOutput: float = 0, exponent: float = 1)

Constructor for QgsGenericNumericTransformer.

Parameters:

minValue (float = 0) – minimum expected input value
maxValue (float = 1) – maximum expected input value
minOutput (float = 0) – minimum value to return
maxOutput (float = 1) – maximum value to return
nullOutput (float = 0) – value to return for null inputs
exponent (float = 1) – optional exponential for non-linear scaling

__init__(a0: QgsGenericNumericTransformer)

Parameters:: a0 (QgsGenericNumericTransformer)

exponent(self) → float[source]¶

Returns the exponent for an exponential expression.

See also

setExponent()

Return type:: float

static fromExpression(expression: str | None)[source]¶

Attempts to parse an expression into a corresponding QgsSizeScaleTransformer.

Parameters:

expression (Optional[str]) -> (Optional[QgsGenericNumericTransformer]) – expression to parse

Returns:

corresponding QgsSizeScaleTransformer, or None if expression could not be parsed to a size scale transformer.
baseExpression: the component of the source expression which is used to calculate the input to the property transformer. This will be set to an empty string if a field reference is the transformer input.
fieldName: a field name which is used to calculate the input to the property transformer. This will be set to an empty string if an expression is the transformer input.

maxOutputValue(self) → float[source]¶

Returns the maximum calculated size.

See also

minOutputValue()