Classifications

You can use any of these classification method classes:

• QgsClassificationQuantile()
• QgsClassificationEqualInterval()
• QgsClassificationJenks()
• QgsClassificationPrettyBreaks()
• QgsClassificationLogarithmic()
• QgsClassificationStandardDeviation()

Available color ramps

You can check all the ramps availables in your QGIS like that:

default_style = QgsStyle().defaultStyle()
available_ramps = default_style.colorRampNames()
for ramp in available_ramps:
    print(ramp)

Equal intervals

# Set layer name and desired params
ramp_name = 'Spectral'
value_field = 'Population (2024)'
num_classes = 10
classification_method = QgsClassificationEqualInterval()
 
layer = QgsProject().instance().mapLayersByName('Countries')[0]
 
format = QgsRendererRangeLabelFormat()
format.setTrimTrailingZeroes(True)
 
default_style = QgsStyle().defaultStyle()
 
color_ramp = default_style.colorRamp(ramp_name)
 
renderer = QgsGraduatedSymbolRenderer()
renderer.setClassAttribute(value_field)
renderer.setClassificationMethod(classification_method)
renderer.setLabelFormat(format)
renderer.updateClasses(layer, num_classes)
 
renderer.updateColorRamp(color_ramp)
 
layer.setRenderer(renderer)
layer.triggerRepaint()

Jenks

# Set layer name and desired params
ramp_name = 'PuRd'
value_field = 'Population (2024)'
num_classes = 20
classification_method = QgsClassificationJenks()
 
layer = QgsProject().instance().mapLayersByName('Countries')[0]
 
format = QgsRendererRangeLabelFormat()
format.setTrimTrailingZeroes(True)
 
default_style = QgsStyle().defaultStyle()
 
color_ramp = default_style.colorRamp(ramp_name)
 
renderer = QgsGraduatedSymbolRenderer()
renderer.setClassAttribute(value_field)
renderer.setClassificationMethod(classification_method)
renderer.setLabelFormat(format)
renderer.updateClasses(layer, num_classes)
 
renderer.updateColorRamp(color_ramp)
 
layer.setRenderer(renderer)
layer.triggerRepaint()

Round zeroes

format = QgsRendererRangeLabelFormat()
format.setTrimTrailingZeroes(True)

Decimals

format = QgsRendererRangeLabelFormat()
format.setPrecision(2)

Separator

format = QgsRendererRangeLabelFormat()
format.setFormat("%1 - %2")

Invert colors

color_ramp = default_style.colorRamp(ramp_name)
 
# Manually invert the color ramp
if isinstance(color_ramp, QgsGradientColorRamp):
    inverted_ramp = QgsGradientColorRamp(
        color_ramp.color2(), # Use the second color as the start color
        color_ramp.color1() # Use the first color as the end color
    )
else:
    inverted_ramp = color_ramp
...
renderer.updateColorRamp(inverted_ramp)