Prepare TXT file from vector data using python in QGIS
Here is code :
layer = iface.activeLayer()
features = layer.getFeatures()
district_area = QgsDistanceArea()
district_area.setEllipsoid('WGS84')
total_area = 0
with open('D:/your_folder_path/areas.txt','w') as f:
for feature in features:
name = feature['ADM2_EN']
geom = feature.geometry()
area = district_area.measureArea(geom) / (1000*1000) # it give you square km
print(area)

total_area = total_area + area
f.write(f"Area of distict name {name} is {area:.2f} square kilometers\n")
print(total_area)