写入几何

使用插入和更新游标，您可以使用脚本在要素类中创建要素或更新现有要素。 脚本可以通过创建 Point 对象、填充要素属性和将要素放入 Array 中来定义要素。 然后，即可通过 Polygon、Polyline、PointGeometry 或 Multipoint 几何类使用该数组来设置要素几何。

import arcpy

fc = "c:/data/gdb.gdb/roads"
cursor = arcpy.da.InsertCursor(fc, ["SHAPE@"])
array = arcpy.Array(
    [arcpy.Point(-77.4349451, 37.5408265), arcpy.Point(-78.6384349, 35.7780943)]
)
spatial_reference = arcpy.SpatialReference(4326)
polyline = arcpy.Polyline(array, spatial_reference)

cursor.insertRow([polyline])

如上所示，单个几何部分可以由点数组定义。 同样，可以使用同一游标从点数组的数组创建多部件要素，如下所示。

import arcpy

first_part = arcpy.Array(
    [arcpy.Point(-77.4349451, 37.5408265), arcpy.Point(-78.6384349, 35.7780943)]
)
second_part = arcpy.Array(
    [arcpy.Point(-79.7910143, 36.0786785), arcpy.Point(-80.8546435, 35.2315402)]
)

array = arcpy.Array([first_part, second_part])
spatial_reference = arcpy.SpatialReference(4326)
multipart_feature = arcpy.Polyline(array, spatial_reference)

cursor.insertRow([multipart_feature])

编写点要素时，仅使用单个点对象来设置点要素的几何。 使用 SHAPE@XY 令牌（以及 SHAPE@M 和 SHAPE@Z 令牌（如果需要的话）），可以更加轻松（而且高效）地创建点。

import arcpy

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

    cursor.insertRow([xy])

使用 SHAPE@ 令牌也可编写点。

import arcpy

with arcpy.da.UpdateCursor(
    "Shops", ["SHAPE@", "ST_ADDRESS", "ZIP"], where_clause="NAME = 'The Cupcakery'"
) as cursor:
    for row in cursor:
        pt = arcpy.Point(-117.18854177699995, 34.06044265100007)
        row = [pt, "540 W Stuart Ave", 92374]
        cursor.updateRow(row)

所有几何在写入要素类之前都经过验证。 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）。

以下示例显示如何读取包含一系列线性坐标的坐标组（由 coords_list 定义），并使用它们创建要素类。

# 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
import os

# List of coordinates (ID, X, Y)
coords_list = [
    [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.management.CreateFeatureclass(
        os.path.dirname(outFC), os.path.basename(outFC), "POLYLINE", template
    )

    # Access spatial reference of template to define spatial
    # reference of geometries
    spatial_reference = arcpy.Describe(template).spatialReference

    # 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 coords_list:
        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
    polyline = arcpy.Polyline(array, spatial_reference)
    cur.insertRow([polyline])


except Exception as e:
    print(e)
finally:
    # Clean up the cursor if necessary
    if cur:
        del cur

在以下示例中，现有元素与新要素组合，现有要素使用组合要素更新。

import arcpy

array = arcpy.Array(
    [
        arcpy.Point(-117.1723261, 34.0240298),
        arcpy.Point(-117.1722951, 34.0240060),
        arcpy.Point(-117.1719831, 34.0240465),
        arcpy.Point(-117.1716733, 34.0241251),
    ]
)

with arcpy.da.UpdateCursor(
    "HikingTrails", ["SHAPE@"], where_clause="TRAILNAME = 'Sunset Ridge Trail'"
) as cursor:
    for row in cursor:
        new_polyline = arcpy.Polyline(array)
        row[0] = row[0].union(new_polyline)
        cursor.updateRow(row)

要创建多部分面要素和折线要素以及带有内部环的面要素，需要先创建由数组构成的数组。 然后将其传递到 Polygon 和 Polyline 类。

根据坐标列表创建几何

也可以根据坐标列表创建几何。 这种方法可以提高性能，因为其可免除创建几何对象的消耗。 但是，仅限于单部件要素；对于面要素，则没有内部环。 所有坐标应该以要素类的空间参考为单位。

在以下示例中，将根据 x,y 对列表创建单个折线要素。

import arcpy

coordinates = [
    (-117.2000424, 34.0555514),
    (-117.2000788, 34.0592066),
    (-117.1957315, 34.0592309),
    (-117.1956951, 34.0556001),
]

# Create a feature class with a spatial reference of GCS WGS 1984
result = arcpy.management.CreateFeatureclass(
    arcpy.env.scratchGDB, "esri_square", "POLYLINE", spatial_reference=4326
)
feature_class = result[0]

# Write feature to new feature class
with arcpy.da.InsertCursor(feature_class, ["SHAPE@"]) as cursor:
    cursor.insertRow([coordinates])

类似地，在以下示例中，将根据 x,y,z 坐标的列表创建单个 3D 折线要素。

import arcpy

coordinates = [
    (-117.2000424, 34.0555514, 1),
    (-117.2000788, 34.0592066, 2),
    (-117.1957315, 34.0592309, 5),
    (-117.1956951, 34.0556001, 2),
]

# Create a feature class with a spatial reference of GCS WGS 1984
result = arcpy.management.CreateFeatureclass(
    arcpy.env.scratchGDB,
    "esri_square_z",
    "POLYLINE",
    has_z="ENABLED",
    spatial_reference=4326,
)
feature_class = result[0]

# Write feature to new feature class
with arcpy.da.InsertCursor(feature_class, ["SHAPE@"]) as cursor:
    cursor.insertRow([coordinates])