Counting points within polygon using PyQGIS?

Question

I have one polygon and onde shp of points (some within and others without the polygon). I have tried the following code:

layers = QgsProject.instance().mapLayers()

for feature in layers['poly_teste_1'].getFeatures():
    geom_poly=feature.geometry()

for feature2 in layers['points_test2_2'].getFeatures():
    geom_point=feature2.geometry()
i=0
for points in layers['pointo_test2_2'].getFeatures():
    if geom_poly.contains(geom_point):
        i=i+1


print(i)

The problem is that the code a printing the total number of points, and not only the ones that are within the polygon.

Answer 1

(in the second loop) : you assign geom_point the geometry of the last point found in your point layer (last of the loop, depending of your table's objects order ...)

(In the third loop) : you 'play' with this geom_point which is "a" point (obviously in your polygon) but you're not iterating over all the points of your point layer.

That's not a gis issue but a programming issue ...

Answer 2

A simple way can be use the processing algorithms "Select by location", where PREDICATE: [6] means "are within"

processing.run("native:selectbylocation", {'INPUT':point_layer,'PREDICATE':[6],'INTERSECT':polygon_layer,'METHOD':0})
point_layer.selectedFeatureCount()