写入几何

通过使用插入和更新游标，脚本可以在要素类中创建新要素或更新现有要素。脚本可以通过创建点对象、填充要素属性和将要素放入数组中来定义要素。该数组随后即可用于设置要素的几何。单个几何部分可以由点数组定义，因此可以从多个点数组创建多部分 (multipart) 要素。

下面就是一个文件示例，该示例将由随后的脚本进行处理。它包含一个点 ID 及 x 坐标和 y 坐标。

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

以下示例显示如何读取包含一系列线性坐标的文本文件（如上所示），并使用它们创建新要素类。

# 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 and other required modules
#
import arcpy
from arcpy import env
import fileinput
import string
import os

env.overwriteOutput = True

# Get the coordinate ASCII file
#
infile = arcpy.GetParameterAsText(0)

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

# Get the template feature class
#
template = arcpy.GetParameterAsText(2)

try:
   # Create the output feature class
   #
   arcpy.CreateFeatureclass_management(os.path.dirname(fcname),
                                       os.path.basename(fcname), 
                                       "Polyline", template)

   # Open an insert cursor for the new feature class
   #
   cur = arcpy.InsertCursor(fcname)

   # Create an array and point object needed to create features
   #
   lineArray = arcpy.Array()
   pnt = arcpy.Point()

   # Initialize a variable for keeping track of a feature's ID.
   #
   ID = -1 
   for line in fileinput.input(infile): # Open the input file
      # set the point's ID, X and Y properties
      #
      pnt.ID, pnt.X, pnt.Y = string.split(line,";")
      print pnt.ID, pnt.X, pnt.Y
      if ID == -1:
         ID = pnt.ID

      # Add the point to the feature's array of points
      #   If the ID has changed, create a new feature
      #
      if ID != pnt.ID:
         # Create a new row or feature, in the feature class
         #
         feat = cur.newRow()

         # Set the geometry of the new feature to the array of points
         #
         feat.shape = lineArray

         # Insert the feature
         #
         cur.insertRow(feat)
         lineArray.removeAll()
      lineArray.add(pnt)
      ID = pnt.ID

   # Add the last feature
   #
   feat = cur.newRow()
   feat.shape = lineArray
   cur.insertRow(feat)
      
   lineArray.removeAll()
   fileinput.close()
   del cur
except Exception as e:
   print e.message

写入点要素时不需要点数组。单个点对象用于设置点要素几何。

所有几何在写入要素类前都已经过验证。在插入几何前的几何简化过程中，将纠正各类问题（例如，不正确的环方向和自相交面以及其他问题）。

示例：使用 SearchCursor 和 InsertCursor 创建方形缓冲区

某些情况下，最好基于另一个要素类的要素创建新几何。这可以通过同时使用 SearchCursor 和 InsertCursor 来实现。

在以下示例中，InsertCursor 用于标识输入点要素类的 x,y 坐标。这些点坐标用于计算方形缓冲区多边形的拐角位置，这些拐角位置通过 InsertCursor 输入到输出中。

import arcpy
from arcpy import env
import os

env.overwriteOutput = True

# Get arguments: 
#   Input point feature class
#   Output polygon feature class
#   Buffer distance
#   Boolean type: Maintain fields and field values of the input in the output 
#
inPoints   = arcpy.GetParameterAsText(0)
outPolys   = arcpy.GetParameterAsText(1)
bufDist    = arcpy.GetParameterAsText(2)
keepFields = arcpy.GetParameterAsText(3)

# Prepare the output based on whether field and field values are desired in the output
#
if keepFields:
    # Create empty output polygon feature class that includes fields of the input
    #
    arcpy.CreateFeatureClass(os.path.dirname(outPolys), os.path.basename(outPolys), "POLYGON",
                             inPoints, "", "", inPoints)

    # Create a short list of fields to ignore when moving fields values from 
    #  input to output
    #
    ignoreFields = []

    # Use Describe properties to identify the shapeFieldName and OIDFieldName
    #
    desc = arcpy.Describe(inPoints)
    ignoreFields.append(desc.shapeFieldName)
    ignoreFields.append(desc.OIDFieldName)

    # Create a list of fields to use when moving field values from input to output
    #
    fields = arcpy.ListFields(inPoints)
    fieldList = []
    for field in fields:
        if field.name not in ignoreFields:
            fieldList.append(field.name)
else:
    # Create empty output polygon feature class without fields of the input
    #
    arcpy.CreateFeatureclass(os.path.dirname(outPolys), os.path.basename(outPolys), "POLYGON",
                             "", "", "", inPoints)

# Open searchcursor
#
inRows = arcpy.SearchCursor(inPoints)

# Open insertcursor
#
outRows = arcpy.InsertCursor(outPolys)

# Create point and array objects
#
pntObj = arcpy.Point()
arrayObj = arcpy.Array()

for inRow in inRows: # One output feature for each input point feature
    inShape = inRow.shape
    pnt = inShape.getPart(0)

    # Need 5 vertices for square buffer: upper right, upper left, lower left,
    #   lower right, upper right. Add and subtract distance from coordinates of
    #   input point as appropriate.
    for vertex in [0,1,2,3,4]:
        pntObj.ID = vertex
        if vertex in [0,3,4]:
            pntObj.X = pnt.X + bufDist
        else:
            pntObj.X = pnt.X - bufDist
        if vertex in [0,1,5]:
            pntObj.Y = pnt.Y + bufDist
        else:
            pntObj.Y = pnt.Y - bufDist
        arrayObj.add(pntObj)

    # Create new row for output feature
    #
    feat = outRows.newRow()

    # Shift attributes from input to output
    #
    if keepFields == "true":
        for fieldName in fieldList:
            feat.setValue(fieldName, inRow.getValue(fieldName))
    
    # Assign array of points to output feature
    #
    feat.shape = arrayObj

    # Insert the feature
    #
    outRows.insertRow(feat)

    # Clear array of points
    #
    arrayObj.removeAll()

# Delete inputcursor
#
del outRows

注：

仅仅使用地理处理工具，也可以先后通过缓冲和 FeatureEnvelopeToPolygon 工具计算方形缓冲区。