ArcGIS Help 10.1 - Writing geometries

Using insert and update cursors, scripts can create new features in a feature class or update existing ones. A script can define a feature by creating a Point object, populating its properties, and placing it in an Array. That array can then be used to set a feature's geometry using Polygon, Polyline, PointGeometry, or MultiPoint geometry classes.

import arcpy
fc = "c:/data/gdb.gdb/roads"
cursor = arcpy.da.InsertCursor(fc, ["SHAPE@"])
array = arcpy.Array([arcpy.Point(5997611.48964, 2069897.7022),
                     arcpy.Point(5997577.46097, 2069905.81145)])
polyline = arcpy.Polyline(array)

cursor.insertRow([polyline])

As shown above, a single geometry part is defined by an array of points. Likewise, a multipart feature can be created from an array of arrays of points as shown below using the same cursor.

firstPart = arcpy.Array([arcpy.Point(5997624.6225, 2069868.8208),
                         arcpy.Point(5997674.94199, 2069833.81741)])
secondPart = arcpy.Array([arcpy.Point(5997616.44497, 2069862.32774),
                          arcpy.Point(5997670.57373, 2069824.67456)])

array = arcpy.Array([firstPart, secondPart])
multipartFeature = arcpy.Polyline(array)

cursor.insertRow([newGeometry2])

When writing point features, only a single point object is used to set the geometry of a point feature. Points can also be created more easily (and efficiently) using the SHAPE@XY token (and SHAPE@M and SHAPE@Z tokens, as needed).

import arcpy

# fc is a point feature class
#
fc = "c:/data/gdb.gdb/stops"
cursor = arcpy.da.InsertCursor(fc, ["SHAPE@XY"])
xy = (5997594.4753, 2069901.75682)

cursor.insertRow([xy])

All geometries are validated before they are written to a feature class. Issues such as incorrect ring orientation and self-intersecting polygons, among others, are corrected when the geometry is simplified before its insertion.

The following example shows how to read a set of coordinates (defined by coordsList) containing a series of linear coordinates and use them to create a new feature class.

# Create a new line feature class using a text file of coordinates.
#   Each coordinate entry is semicolon delimited in the format of ID;X;Y
import arcpy
import os

# List of coordinates (ID, X, Y)
#
coordsList = [[1, -61845879.0968, 45047635.4861], 
              [1, -3976119.96791, 46073695.0451],
              [1, 1154177.8272, -25134838.3511],
              [1, -62051091.0086, -26160897.9101],
              [2, 17365918.8598, 44431999.7507],
              [2, 39939229.1582, 45252847.3979],
              [2, 41170500.6291, 27194199.1591],
              [2, 17981554.5952, 27809834.8945],
              [3, 15519011.6535, 11598093.8619],
              [3, 52046731.9547, 13034577.2446],
              [3, 52867579.6019, -16105514.2317],
              [3, 17160706.948, -16515938.0553]]

# The output feature class to be created
#
outFC = arcpy.GetParameterAsText(0)

# Get the template feature class
#
template = arcpy.GetParameterAsText(1)

cur = None
try:
    # Create the output feature class
    #
    arcpy.CreateFeatureclass_management(os.path.dirname(outFC),
                                        os.path.basename(outFC), 
                                        "POLYLINE", template)

    # Open an insert cursor for the new feature class
    #
    cur = arcpy.da.InsertCursor(outFC, ["SHAPE@"])

    # Create an array object needed to create features
    #
    array = arcpy.Array()

    # Initialize a variable for keeping track of a feature's ID.
    #
    ID = -1
    for coords in coordsList: 
        if ID == -1:
            ID = coords[0]

        # Add the point to the feature's array of points
        #   If the ID has changed, create a new feature
        #
        if ID != coords[0]:
            cur.insertRow([arcpy.Polyline(array)])
            array.removeAll()
        array.add(arcpy.Point(coords[1], coords[2], ID=coords[0]))
        ID = coords[0]

    # Add the last feature
    #
    cur.insertRow([arcpy.Polyline(array)])


except Exception as e:
   print e.message
finally:
    # Cleanup the cursor if necessary
    #
    if cur:
        del cur

Multipart polygon and polyline features and polygon features with interior rings can be created by creating an array of arrays and passing that to Polygon and Polyline classes.

Writing geometries

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