ArcPy – How to Cut Polygon Using Line and Cutter in ArcGIS 10.2

Question

What I'd like to do, using ArcPy: use a line to split a bunch of polygons into separate parts.
Here is what the inputs could look like:

In this case the line should split each polygon into two separate polygons, creating 6 separate polygons in the end.

This question has been asked many times, and there have been a lot of answers provided, but none of them seem to mention the polygon's cut method, perhaps because it seems to only have been introduced in 10.2.

Here is what the ArcGIS Help shows (scroll to cut (cutter)):

This seems to be exactly what I need, but I cannot entirely figure out how to implement it.

From the few examples I was able to find, it seems like I cannot use the method directly on a shapefile that I am referencing, but I need to access the underlying geometry/vertices, so here is what I did (please correct me if there is an entirely different way of doing it):

• read shapefile's vertices using a cursor
• push each vertex into an array
• use that array to create a polygon/line

The next step would be to to use the cut() method, as shown in the screenshot above, to actually split the polygons, but I cannot get it to work.

What follows is my code (only the polygon-part uses comments as the polyline is just repetition):

import arcpy

polygon = r"D:\Data\poly.shp"
line = r"D:\Data\line.shp"

# ------------------- POLYGON -------------------
# first read the geometry
# i.e.: read all of the vertex coordinates, and push them into an array
dataset_vertices = []

# loop through each feature
for row in arcpy.da.SearchCursor(polygon, ["OID@", "SHAPE@"]):
    print("Here comes feature {0}:".format(row[0]))
    partnum = 0
    # Step through each part of the feature
    for part in row[1]:
        # Print the part number
        print("Part {0}:".format(partnum))

        tempPart = [] # push each vertex into an array
        # Step through each vertex in the feature
        for pnt in part:
            if pnt:
                # Print x,y coordinates of current point
                print("{0}, {1}".format(pnt.X, pnt.Y))
                tempPart.append([pnt.X,pnt.Y])
            else:
                # If pnt is None, this represents an interior ring
                print("Interior Ring:")
        # push part-array into entire array
        dataset_vertices.append(tempPart)
        partnum += 1


# A list that will hold each the Polygon objects
polygon_features = []

for feature in dataset_vertices:
    # Create a Polygon object based on the array of points
    # Append to the list of Polygon objects
    polygon_features.append(
        arcpy.Polygon(
            arcpy.Array([arcpy.Point(*coords) for coords in feature])))

# ------------------- POLYLINE -------------------
line_vertices = []

for row in arcpy.da.SearchCursor(line, ["OID@", "SHAPE@"]):
    print("Here comes feature {0}:".format(row[0]))

    partnum = 0
    for part in row[1]:
        print("Part {0}:".format(partnum))

        tempPart = []
        for pnt in part:
            if pnt:
                print("{0}, {1}".format(pnt.X, pnt.Y))
                tempPart.append([pnt.X,pnt.Y])
            else:
                print("Interior Ring:")
        line_vertices.append(tempPart)
        partnum += 1


line_features = []

for feature in dataset_vertices:
    line_features.append(
        arcpy.Polygon(
            arcpy.Array([arcpy.Point(*coords) for coords in feature])))

After running this code I can use methods, such as polygon_features[0].boundary(), but I am not sure how to use cut().

Answer 1

Feature To Polygon will slice polygons by line feature classes when you use the two feature classes as its input.

Inputs:

Results:

Depending on line geometry this method can create excess polygons. If so, clip your output feature class by your original input polygon feature class to eliminate the new polygons.

If you only want certain polygons sliced by certain lines, use an SQL expression and feature layers to limit your inputs.