Class: QgsRuleBasedLabeling¶

Rule based labeling for a vector layer.

Class Hierarchy¶

Base classes¶

QgsAbstractVectorLayerLabeling

Abstract base class - its implementations define different approaches to the labeling of a vector layer.

Methods

rootRule

Static Methods

create

Create the instance from a DOM element with saved configuration

class qgis.core.QgsRuleBasedLabeling[source]¶

Bases: QgsAbstractVectorLayerLabeling

__init__(root: QgsRuleBasedLabeling.Rule | None)

Constructs the labeling from given tree of rules (takes ownership)

Parameters:: root (Optional[QgsRuleBasedLabeling.Rule])

class Rule[source]¶

Bases: object

A child rule for QgsRuleBasedLabeling.

QgsRuleBasedLabeling.Rule(settings: Optional[QgsPalLayerSettings], maximumScale: float = 0, minimumScale: float = 0, filterExp: Optional[str] = ‘’, description: Optional[str] = ‘’, elseRule: bool = False) takes ownership of settings, settings may be None

Filtered = 0¶

Inactive = 1¶

class RegisterResult¶: Bases: int

Registered = 2¶

active(self) → bool[source]¶

Returns if this rule is active

Return type:: bool
Returns:: True if the rule is active

appendChild(self, rule: QgsRuleBasedLabeling.Rule | None)[source]¶

add child rule, take ownership, sets this as parent

Parameters:: rule (Optional[QgsRuleBasedLabeling.Rule])

children(self) → List[QgsRuleBasedLabeling.Rule]¶

Returns all children rules of this rule

Return type:: List[QgsRuleBasedLabeling.Rule]
Returns:: A list of rules

static create(ruleElem: QDomElement, context: QgsReadWriteContext, reuseId: bool = True) → QgsRuleBasedLabeling.Rule | None[source]¶

Create a rule from an XML definition

Parameters:

ruleElem (QDomElement) – The XML rule element
context (QgsReadWriteContext) – reading context
reuseId (bool = True) – set to True to create an exact copy of the original symbol or False to create a new rule with the same parameters as the original but a new unique ruleKey(). (Since QGIS 3.30)

Return type:

Optional[QgsRuleBasedLabeling.Rule]

Returns:

A new rule

dependsOnScale(self) → bool[source]¶

Determines if scale based labeling is active

Return type:: bool
Returns:: True if scale based labeling is active

descendants(self) → List[QgsRuleBasedLabeling.Rule][source]¶

Returns all children, grand-children, grand-grand-children, grand-gra… you get it

Return type:: List[QgsRuleBasedLabeling.Rule]
Returns:: A list of descendant rules

description(self) → str[source]¶

A human readable description for this rule

Return type:: str
Returns:: Description

filterExpression(self) → str[source]¶

A filter that will check if this rule applies

Return type:: str
Returns:: An expression

findRuleByKey(self, key: str | None) → QgsRuleBasedLabeling.Rule | None[source]¶

Try to find a rule given its unique key

Parameters:: key (Optional[str])
Return type:: Optional[QgsRuleBasedLabeling.Rule]

insertChild(self, i: int, rule: QgsRuleBasedLabeling.Rule | None)[source]¶

add child rule, take ownership, sets this as parent

Parameters:

i (int)
rule (Optional[QgsRuleBasedLabeling.Rule])

isElse(self) → bool[source]¶

Check if this rule is an ELSE rule

Return type:: bool
Returns:: True if this rule is an else rule

maximumScale(self) → float[source]¶

Returns the maximum map scale (i.e. most “zoomed in” scale) at which the label rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no maximum scale visibility.

See also

minimumScale()

See also

setMaximumScale()

Return type:: float

minimumScale(self) → float[source]¶

Returns the minimum map scale (i.e. most “zoomed out” scale) at which the label rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no minimum scale visibility.

See also

maximumScale()

See also

setMinimumScale()

Return type:: float

parent(self) → QgsRuleBasedLabeling.Rule | None[source]¶

The parent rule

Return type:: Optional[QgsRuleBasedLabeling.Rule]
Returns:: Parent rule

removeChildAt(self, i: int)[source]¶

delete child rule

Parameters:: i (int)

ruleKey(self) → str[source]¶

Unique rule identifier (for identification of rule within labeling, used as provider ID)

Return type:: str

setActive(self, state: bool)[source]¶

Sets if this rule is active

Parameters:: state (bool) – Determines if the rule should be activated or deactivated

setDescription(self, description: str | None)[source]¶

Set a human readable description for this rule

Parameters:: description (Optional[str]) – Description

setFilterExpression(self, filterExp: str | None)[source]¶

Set the expression used to check if a given feature shall be rendered with this rule

Parameters:: filterExp (Optional[str]) – An expression

setIsElse(self, iselse: bool)[source]¶

Sets if this rule is an ELSE rule

Parameters:: iselse (bool) – If True, this rule is an ELSE rule

setMaximumScale(self, scale: float)[source]¶

Sets the maximum map scale (i.e. most “zoomed in” scale) at which the rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no maximum scale visibility.

See also

maximumScale()

See also

setMinimumScale()

Parameters:: scale (float)

setMinimumScale(self, scale: float)[source]¶

Sets the minimum map scale (i.e. most “zoomed out” scale) at which the label rule will be active. The scale value indicates the scale denominator, e.g. 1000.0 for a 1:1000 map. A scale of 0 indicates no minimum scale visibility.

See also

minimumScale()

See also

setMaximumScale()