To sum up all features' areas can be done either via

To sum up only selected features' areas can be done either via:

aggregate() method of the QgsVectorLayer class

or calculate() method of the QgsAggregateCalculator class

To sum up all features' areas can be done either via

To sum up only selected features' areas can be done either via:

the aggregate() method of the QgsVectorLayer class:

or the calculate() method of the QgsAggregateCalculator class:

aggregate method of the QgsVectorLayer class

or calculate method of the QgsAggregateCalculator class

aggregate() method of the QgsVectorLayer class

or calculate() method of the QgsAggregateCalculator class

To sum up all features' areas can be done either via

the "FIELD_NAME" field, that contains area values:

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of all features
area_total_sum = layer.aggregate(QgsAggregateCalculator.Sum, "FIELD_NAME")

print(area_total_sum) # (19594.140492000002, True)

or the $area variable directly:

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of all features
area_total_sum = layer.aggregate(QgsAggregateCalculator.Sum, "$area")

print(area_total_sum) # (19594.140491519036, True)

If one applies this expression area($geometry) the result will be slightly different (19603.3203125, True). Therefore, pay attention to this thread: Calculating polygon areas in shapefile using QGIS.

To sum up only selected features' areas can be done either via:

aggregate method of the QgsVectorLayer class

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of selected features
area_selected_sum = layer.aggregate(
                            aggregate=QgsAggregateCalculator.Sum,
                            fieldOrExpression="FIELD_NAME",
                            fids=layer.selectedFeatureIds()
                            )

print(area_selected_sum) # (1958.09388, True)

or calculate method of the QgsAggregateCalculator class

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# constructing the aggregate calculator
agg_calc = QgsAggregateCalculator(layer)
# setting a filter for selected features only
agg_calc.setFidsFilter(layer.selectedFeatureIds())

# summing area of selected features
area_selected_sum = agg_calc.calculate(QgsAggregateCalculator.Sum, "FIELD_NAME")

print(area_selected_sum) # (1958.09388, True)

As was already previously shown, instead of the "FIELD_NAME" one can also use either $area or area($geometry).

References:

• Summing values in one field using PyQGIS

To sum up all features' areas can be done either via

the "FIELD_NAME" field, that contains area values:

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of all features
area_total_sum = layer.aggregate(QgsAggregateCalculator.Sum, "FIELD_NAME")

print(area_total_sum) # (19594.140492000002, True)

or the $area variable directly:

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of all features
area_total_sum = layer.aggregate(QgsAggregateCalculator.Sum, "$area")

print(area_total_sum) # (19594.140491519036, True)

Then if necessary proceed with area_total_sum[0] * 5.

If one applies this expression area($geometry) the result will be slightly different (19603.3203125, True). Therefore, pay attention to this thread: Calculating polygon areas in shapefile using QGIS.

To sum up only selected features' areas can be done either via:

aggregate method of the QgsVectorLayer class

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# summing area of selected features
area_selected_sum = layer.aggregate(
                            aggregate=QgsAggregateCalculator.Sum,
                            fieldOrExpression="FIELD_NAME",
                            fids=layer.selectedFeatureIds()
                            )

print(area_selected_sum) # (1958.09388, True)

or calculate method of the QgsAggregateCalculator class

# imports
from qgis.core import QgsProject, QgsAggregateCalculator

# getting polygon layer by its name
layer = QgsProject.instance().mapLayersByName("YOUR_LAYER_NAME")[0]

# constructing the aggregate calculator
agg_calc = QgsAggregateCalculator(layer)
# setting a filter for selected features only
agg_calc.setFidsFilter(layer.selectedFeatureIds())

# summing area of selected features
area_selected_sum = agg_calc.calculate(QgsAggregateCalculator.Sum, "FIELD_NAME")

print(area_selected_sum) # (1958.09388, True)

As was already previously shown, instead of the "FIELD_NAME" one can also use either $area or area($geometry).

Then if necessary proceed with area_selected_sum[0] * 5.

References:

• Summing values in one field using PyQGIS