lyr = ds.GetLayerByName('somelayer')
lyr.ResetReading()
point = ogr.CreateGeometryFromWkt('POINT(4 5)')
for feat in lyr:
    geom = feat.GetGeometryRef()
if geom.Contains(point):
    sm = feat.GetField(feat.GetFieldIndex('surface_material'))
How to use python to lookup information at specific latitude/longitude in a ESRI shapefile?