Monday, June 6, 2011

Polygon Objects

The Polygon object is simply a collection of X,Y coordinates that form a closed shape in a connected sequence.

To create a polygon object, you need a List or Array of Points passed during instantiation at minimum.  There are 3 optional parameters: spatial reference, hasZ and hasM.  Here is more detailed explaination below:

This screen shot from the help in ArcGIS explains in details what each property and syntax means.  I do not need to really go into this because I assume everyone can read. The methods overview can be found here.

Example: Creating a Polygon Object From a List of Coordinates

import arcpy

# Triangle Coordinate List
cList = [[1,2],[2,2], [1,4]]

# Create a Point Object and Array
point = arcpy.Point()
array = arcpy.Array()

for feat in cList:
   point.X = feat[0]
   point.Y = feat[1]
   point = arcpy.Point()

# Close the shape

# Create the polygon
polygon = arcpy.Polygon(array)