Using geometry objects with geoprocessing tools

Using geometry objects with geoprocessing tools

In many geoprocessing workflows, you may need to run a specific operation using coordinate and geometry information but don't necessarily want to go through the process of creating a new (temporary) feature class, populating the feature class with cursors, using the feature class, then deleting the temporary feature class. Geometry objects can be used instead for both input and output to make geoprocessing easier. Geometry objects can be created from scratch using Geometry, Multipoint, PointGeometry, Polygon, or Polyline classes.

Using geometry as input

The following sample creates a polygon geometry object created using a list of x,y coordinates. The Clip tool is then used to clip a feature class with the polygon geometry object.

import arcpy

 

# List of coordinates.

coordinates = [

    [2365000, 7355000],

    [2365000, 7455000],

    [2465000, 7455000],

    [2465000, 7355000]]

 

# Create an array with a point object for each coordinate pair

array = arcpy.Array([arcpy.Point(x, y) for x, y in coordinates])

 

# Create a polygon geometry object using the array object

boundary = arcpy.Polygon(array, arcpy.SpatialReference(2953))

 

# Use the geometry to clip an input feature class

arcpy.Clip_analysis('c:/data/rivers.shp', 

                    boundary, 

                    'c:/data/rivers_clipped.shp')

Outputting geometry objects

Output geometry objects can be created by setting the output of a geoprocessing tool to an empty geometry object. When a tool runs when set to an empty geometry object, the tool returns a list of geometry objects. In the following example, the Copy Features tool is used to return a list of geometry objects, which can then be looped through to accumulate the total length of all features.

import arcpy

 

# Run the CopyFeatures tool, setting the output to a geometry object.  

#  geometries is returned as a list of geometry objects.

#  

geometries = arcpy.CopyFeatures_management('c:/temp/outlines.shp', arcpy.Geometry())

 

# Walk through each geometry, totaling the length

#

length = sum([g.length for g in geometries])

print('Total length: {}'.format(length))