Calculating main_angle of polygons using PyQGIS

Question

According to Calculating Polygon Main Angle using QGIS, it is possible to find the main_angle of a polygon by using a field expression like:

main_angle($geometry)

Can this function be called using PyQGIS but not as an expression but from the Python console or script as a way to get the main orientation angle of a polygon?

Answer 1

See: PyQGIS 101: Using expressions to compute new field values

layer = iface.activeLayer()
    
expression1 = QgsExpression('main_angle($geometry)')
context = QgsExpressionContext()
context.appendScopes(QgsExpressionContextUtils.globalProjectLayerScopes(layer))
angles = []
for f in layer.getFeatures():
    context.setFeature(f)
    mainangle = expression1.evaluate(context)
    angles.append(mainangle)

print(angles[:5])
#[159.525122844183, 48.41639305999172, 0.7305299973963884, 105.59960002436623, 157.79005356043308]

Answer 2

Another method in addition to @BERA:

layer = iface.activeLayer()
feats = layer.getFeatures()
for f in feats:
    geom = QgsGeometry(f.geometry())
    output_geometry, area, angle, width, height = geom.orientedMinimumBoundingBox()
    print(angle)