geometrypolygonqgisvertices
I have transformed a .dxf-file into a polygon shapefile. In many of the polygons I have lines which do not belong there but I can not delete them as I normally delete vertices on polygons by selecting it and pressing the delete key.
Here is an image (the lines which I want to delete are circled in red).
In order to solve your problem:
At this time you can edit the feature class to remove errors.
The key is the difference method on geometry objects. The following code is far from efficient, since a new update cursor is opened for each polygon. But it has the added benefit of supporting multiple polygons on the same line:
import itertools, arcpy
arcpy.env.overwriteOutput = True
line_FC = r'<path to lines>'
poly_FC = r'<path to polygons>'
output = r'<path to result>'
#clone input lines to memory for fast processing
temp = arcpy.CopyFeatures_management(line_FC, "in_memory/temp")
polygons = arcpy.CopyFeatures_management(poly_FC, arcpy.Geometry())
for poly in polygons:
with arcpy.da.UpdateCursor(temp, ["SHAPE@"]) as uCursor:
for line in uCursor:
line = line[0]
diff = line.difference(poly)
#if the two lines are not equal, that means it intersected the polygon
if not line.equals(diff):
#the result of geometry.difference() is a multipart line of only those
#parts that lie outside the polyon
parts = diff.getPart()
#if parts is empty that means the line is completely within the polygon
#i.e., no difference
if parts:
#We'll need to "join" the end of part1 to the beginning of part2
#so we'll just flatten the list of lists
joined = list(itertools.chain.from_iterable(parts))
#and create a new polyline object to update the shape
poly_trimmed = arcpy.Polyline(arcpy.Array(joined))
uCursor.updateRow([poly_trimmed])
arcpy.CopyFeatures_management(temp, output)
I haven't tested it with edge cases, but this should get you started.
Best Answer
Those lines and vertices are actually holes or islands on your polygon.
Try using the delete part or delete ring tools in the advanced digitizing toolbar, and click on one of the nodes. I have noticed that sometimes you need to drag one or more nodes a bit to be able to click on the hole\island boundaries to delete it.