摘要
用于访问最近设施点网络分析图层中的分析属性。GetSolverProperties 函数用于从最近设施点网络分析图层中获取 ClosestFacilitySolverProperties 对象。
讨论
ClosestFacilitySolverProperties 对象提供对最近设施点网络分析图层中所有分析属性的读取和写入权限。该对象可用于修改最近设施点图层的分析属性,并可重新求解相关图层以确定合适结果。使用创建最近设施点图层地理处理工具可创建新的最近设施点图层。通过从新的最近设施点图层获取 ClosestFacilitySolverProperties 对象,可重新对现有图层进行后续分析,而无需每次分析都创建一个新图层,以节省时间。
修改 ClosestFacilitySolverProperties 对象的属性后,可立即使用其他函数和地理处理工具分析相关图层。无需刷新或更新图层,通过上述对象进行的修改便可生效。
属性
属性 | 说明 | 数据类型 |
accumulators (读写) | Provides the ability to get or set a list of network cost attributes that are accumulated as part of the analysis. An empty list, [], indicates that no cost attributes are accumulated. | String |
attributeParameters (读写) | Provides the ability to get or set the parameterized attributes to be used in the analysis. The property returns a Python dictionary. The dictionary key is a two-value tuple consisting of the attribute name and the parameter name. The value for each item in the dictionary is the parameter value. Parameterized network attributes are used to model some dynamic aspect of an attribute's value. For example, a tunnel with a height restriction of 12 feet can be modeled using a parameter. In this case, the vehicle's height in feet should be specified as the parameter value. If the vehicle is taller than 12 feet, this restriction will then evaluate to true, thereby restricting travel through the tunnel. Similarly, a bridge could have a parameter to specify a weight restriction. Attempting to modify the attributeParameters property in place won't result in updated values. Instead, you should always use a new dictionary object to set values for the property. The following two code blocks demonstrate the difference between these two approaches.
| Dictionary |
defaultCutoff (读写) | 用于获取或设置求解程序停止在设施点中搜索给定事件点时对应的默认阻抗值。值 None 用于指定不应使用中断。 | Double |
defaultTargetFacilityCount (读写) | 用于获取或设置要按事件点查找的最近设施点数。 | Integer |
impedance (读写) | 用于获取或设置用作阻抗的网络成本属性。当确定最近设施点和到最近设施点的最佳路径时,该成本属性最小化。 | String |
outputPathShape (读写) | 用于获取或设置求解程序输出的路径要素的形状类型。以下是可能值列表:
| String |
restrictions (读写) | Provides the ability to get or set a list of restriction attributes that are applied for the analysis. An empty list, [], indicates that no restriction attributes are used for the analysis. | String |
solverName (只读) | 返回被用于获取求解程序属性对象的 Network Analyst 图层所引用的求解程序的名称。从 ClosestFacilitySolverProperties 对象访问时,该属性始终返回字符串值最近设施点求解程序。 | String |
timeOfDay (读写) | 用于获取或设置路径应开始或结束的时间和日期。对该值的解释取决于 timeOfDayUsage 属性是设置为 START_TIME 还是 END_TIME。可以用值 None 指定不应使用任何日期和时间。 可使用以下日期来指定一周中的每一天,而无需使用特定的日期。
例如,要指定路径应该在星期一 8:00 a.m 开始或结束,则将值指定为 datetime.datetime(1900, 1, 1, 8,0,0)。 timeZoneUsage 参数指定该日期和时间是 UTC 还是设施点或事件点所在时区。 | DateTime |
timeOfDayUsage (读写) | 控制 timeOfDay 属性的值代表路径的到达时间还是离开时间。以下是可能值列表:
| String |
timeZoneUsage (读写) | 指定 timeOfDay 参数的时区。
无论 timeZoneUsage 如何设置,如果您的设施点和事件点在多个时区中,则工具将强制执行以下规则:
| String |
travelDirection (读写) | 用于获取或设置在分析过程中设施点和事件点之间的行驶方向。以下是可能值列表:
| String |
useHierarchy (读写) | Controls the use of the hierarchy attribute while performing the analysis. The following is a list of possible values:
| String |
uTurns (读写) | Provides the ability to get or set the policy that indicates how the U-turns at junctions that could occur during network traversal between stops are being handled by the solver. The following is a list of possible values:
| String |
方法概述
方法 | 说明 |
applyTravelMode (travel_mode) | 根据出行模式对象更新网络分析图层的分析属性。随后可对更新的网络分析图层进行求解以完成分析。 |
方法
applyTravelMode (travel_mode)
参数 | 说明 | 数据类型 |
travel_mode | 该变量引用一个源自网络数据集的出行模式对象。可通过调用 arcpy.na.GetTravelModes 函数获得出行模式对象的列表。 | Object |
创建网络分析图层后,将为其分配所有分析属性的默认值。可使用从网络分析图层获得的求解程序属性对象更新各个分析属性。出行模式存储了一组预定义的分析设置,用于帮助执行特定分析,例如,步行时间出行模式存储了执行基于时间的步行分析所需的分析设置。
使用 applyTravelMode 方法,可一次性应用在一个出行模式中定义的所有分析设置。在分析属性完成更新后,可对网络分析图层进行求解以完成分析。
如果在更新求解程序属性时出错,例如,当提供的出行模式所引用的属性在当前网络数据集中不存在,或不再适用于创建求解程序属性对象的相应网络分析图层所使用的网络数据集时,不会产生任何异常。此方法将成功执行,但当您尝试求解此类网络分析图层时会出现错误。
如果 travel_mode 参数不引用出行模式对象或字符串,则将产生 TypeError 异常。如果 travel_mode 参数引用字符串并且该字符串无法在内部转换成出行模式对象的有效字符串表示,将产生 ValueError 异常。
代码实例
ClosestFacilitySolverProperties 示例 1(Python 窗口)
该脚本显示如何更新最近设施点网络分析图层,以在不使用中断值的情况下找到三个设施点。它假设已在新地图文档中根据旧金山地区的网络数据集创建了名为 Closest Hospitals 的最近设施点图层。
#Get the closest facility layer object from a layer named "Closest Hospitals" in
#the table of contents
cfLayer = arcpy.mapping.Layer("Closest Hospitals")
#Get the closest facility solver properties object from the closest facility layer
solverProps = arcpy.na.GetSolverProperties(cfLayer)
#Update the properties for the closest facility layer using the closest facility
#solver properties object
solverProps.defaultCutoff = None
solverProps.defaultTargetFacilityCount = 3
ApplyTravelMode 示例 2(工作流)
此脚本显示基于“货运时间”出行模式查找最近设施点的方法。
#Import modules
import os
import arcpy
#Define variables
workspace = "C:/data/SanDiego.gdb"
output_folder = "C:/data/output"
nds = os.path.join(workspace, "Transportation", "Streets_ND")
facilities = os.path.join(workspace, "WeightStations")
incidents = os.path.join(workspace, "RestAreaLocations")
analysis_layer_name = "ClosestFacility"
#Set environment variables
arcpy.env.overwriteOutput = True
#Check out the network analyst extension
arcpy.CheckOutExtension("network")
#Create a new closest facility analysis layer
make_layer_result = arcpy.na.MakeClosestFacilityLayer(nds, analysis_layer_name,
"TravelTime")
analysis_layer = make_layer_result.getOutput(0)
#Add facilities and incidents to the analysis layer using default field mappings
sub_layer_names = arcpy.na.GetNAClassNames(analysis_layer)
facility_layer_name = sub_layer_names["Facilities"]
incident_layer_name = sub_layer_names["Incidents"]
arcpy.na.AddLocations(analysis_layer, facility_layer_name, facilities, "#", "#")
arcpy.na.AddLocations(analysis_layer, incident_layer_name, incidents, "#", "#")
#Get the Trucking Time travel mode from the network dataset
travel_modes = arcpy.na.GetTravelModes(nds)
trucking_mode = travel_modes["Trucking Time"]
#Apply the travel mode to the analysis layer
solver_properties = arcpy.na.GetSolverProperties(analysis_layer)
solver_properties.applyTravelMode(trucking_mode)
#Solve the analysis layer and save the result as a layer file
arcpy.na.Solve(analysis_layer)
output_layer = os.path.join(output_folder, analysis_layer_name + ".lyr")
arcpy.management.SaveToLayerFile(analysis_layer, output_layer, "RELATIVE")
arcpy.AddMessage("Completed")