Extracting coordinates from multipoint geometries?

Question

I found this guide to get pixel value of raster under point: Getting pixel value of GDAL raster under OGR point without NumPy?

I've a problem here:

for feat in lyr:
    geom = feat.GetGeometryRef()
    mx,my=geom.GetX(), geom.GetY()  #coord in map units

If I print geom, I can see all the point's coordinates but if I print mx or my the result is 0 for every feat.

if I print geom:

MULTIPOINT (9.48556682927651 39.1368546561669)
MULTIPOINT (9.46173837787432 39.1298387934389)
MULTIPOINT (9.54058251881085 39.441437960101)
MULTIPOINT (9.08688113454087 39.5390542536278)
MULTIPOINT (9.00215692841357 39.0072908447031)
MULTIPOINT (9.17741005408364 39.2751570664614)

if i print mx or my:

0.0
0.0
0.0
0.0
0.0
0.0

I'm using Python 3 maybe this could be a problem

Answer 1

You have multipoint data, not points. You need to pull out the point geoms from the multipoints.

Assuming only a single point per multipoint (as per your example):

wkt = 'MULTIPOINT (9.48556682927651 39.1368546561669)'
multipoint = ogr.CreateGeometryFromWkt(wkt )
point = multipoint.GetGeometryRef(0) # <--- Get the point at index 0
print(point.GetX(), point.GetY())

If you don't want to assume only a single point, you can loop through the points in each multipoint:

wkt = 'MULTIPOINT (9.48556682927651 39.1368546561669, 9.46173837787432 39.1298387934389)'
multipoint = ogr.CreateGeometryFromWkt(wkt)
for i in range(multipoint.GetGeometryCount()):
    point = multipoint.GetGeometryRef(i) # <--- Get the geom at index i
    print(point.GetX(), point.GetY())

So when you're looping through the layer, do something like this:

for feat in lyr:
    multipoint = feat.GetGeometryRef()

    point = multipoint.GetGeometryRef(0) # <--- Get the point at index 0
    mx,my = point.GetX(), point.GetY()

    ## OR ##

    for i in range(multipoint.GetGeometryCount()):
        point = multipoint.GetGeometryRef(i) # <--- Get the geom at index i
        mx,my = point.GetX(), point.GetY()

Answer 2

I write this and split the string

geom=feat.GetGeometryRef()
point=geom.Centroid().ExportToWkt() 
mx=float(point.split(' ')[1][1:len(point.split(' ')[1])])
my=float(point.split(' ')[2][0:len(point.split(' ')[2])-1])

Maybe someone will have this problem too