Hello Sean Thanks for you reply. I was also just about to add a follow-up comment.
I upgraded my system to GEOS 3.2.2 (compile from source) and apparently that solved the problem. So I guess it was an issue of libgeos. Can I assume that Shapely 1.2.1 works fine with GEOS 3.2.2 ? I experience no issues at this time, but would appreciate your feedback on this. wbr Emmanuel On Fri, 2010-06-25 at 12:46 +0200, Sean Gillies wrote: > 2010/6/24 Emmanuel Lambert <[email protected]>: > > Hi, > > > > Attached is a list of polygons in WKT format. > > I have a MultiPolygon consisting of these polygons. > > > > The cascaded_union function failes on this multipolygon. > > "ValueError: No Shapely geometry can be created from null value" > > > > Script to reproduce the problem : > > > > from shapely.wkt import loads > > from shapely.geometry import Polygon,MultiPolygon > > from shapely.ops import cascaded_union > > > > f = open('MULTIPOLYGON.TXT','r') > > polygons = [] > > while True: > > wkt = f.readline().replace("\n","") > > print wkt > > if len(wkt)==0: > > break > > pol = loads(wkt) > > polygons.append(pol) > > > > mp = MultiPolygon(polygons) > > up = cascaded_union(mp) > > > > I have tried several strategies to work around it, but cannot get to a > > solution. Is this a bug in shapely, or is something wrong with my data? > > Your advice would be appreciated. > > > > (Shapely 1.2.1) > > > > Thanks, > > > > Emmanuel > > > > Hi Emmanuel, > > Before I try to reproduce this, can you run the script again and > assert that each polygon is valid within the loop? > > pol = loads(wkt) > assert pol.is_valid > polygons.append(pol) > _______________________________________________ Community mailing list [email protected] http://lists.gispython.org/mailman/listinfo/community
