Setting decimal places on labelling using PyQGIS

Question

I'm trying to modify the "Decimal places" (defaut : 3) to "1" from the formatting layer properties.

Here is my code :

background_color = QgsTextBackgroundSettings()
background_color.setEnabled(True)

prop = QgsProperty()
prop.setField("Couleur")
pc = QgsPropertyCollection('ShapeFillColor')
pc.setProperty(58, prop)
layer_settings = QgsPalLayerSettings()
layer_settings.setDataDefinedProperties(pc)

text_format = QgsTextFormat()
text_format.setFont(QFont("MS Shell Dlg 2"))
text_format.setSize(12.5)
text_format.setColor(QColor("black"))
text_format.setFont(QFont("MS Shell Dlg 2",11,QFont.Bold))
text_format.setBackground(background_color)

layer_settings.setFormat(text_format)
layer_settings.fieldName = "NO2"
layer_settings.enabled = True

I think I have to use a function of the class QgsTextFormat but I can’t find which one in the documentary.

Answer 1

Logically, it would be this code, but the checkbox Formatted Numbers isn't checked on my QGIS 3.30 (Windows) :

lyr_no2_concentration = iface.activeLayer()
lyr_settings = QgsPalLayerSettings()
lyr_settings.enabled = True
lyr_settings.fieldName = "NO2"
# code to activate the decimals
lyr_settings.formatNumbers = True  # checkbox
lyr_settings.decimals = 2  # decimals number
# -----------------------------
lyr_no2_concentration.setLabeling(
    QgsVectorLayerSimpleLabeling(lyr_settings)
)
lyr_no2_concentration.triggerRepaint()

See the QgsPalLayerSettings documentation for more details.