Polygon to Line (Data Management) on a Basic License with ArcPy

Glen Bambrick

July 14, 2024
12:33 pm
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Introduction

The Polygon to Line (Data Management) tool is only available in ArcGIS Pro with an Advanced license. You can check out the Esri documentation for this tool here. For now, we will omit the optional identifying neighbouring information and will revisit in the future. A little about this tool; for each input polygon, the boundary will be written out as an enclosed linear feature. A multipart polygon will become a multipart linear feature in the output feature class. The attributes of the input polygon features will be maintained and transferred to the output feature class with a new field add called ORIG_FID. The ORIG_FID will represent the original OID of the input polygon features.

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Syntax

The syntax for the Sort tool is shown below.

				
					arcpy.management.PolygonToLine(
    in_features, 
    out_feature_class,
    {neighbor_option}
)

Import the ArcPy module

ArcPy is a Python site package that enables automation, analysis, and management of geographic data within the ArcGIS software environment.

				
					import arcpy

Define the parameters

Following the Esri documentation, there are two required parameters; in_features (type: Feature Layer) and out_feature_class (type: Feature Class), (and optionally neighbour_option which we are leaving out for now).

				
					## polygon featurer class to convert boundaries to lines
in_features = arcpy.GetParameterAsText(0)
 
## output feature class filepath
out_feature_class = arcpy.GetParameterAsText(1)

Required Python object for the tool

We have a few required objects to help us through the workflow as detailed in the code below.

				
					## srs id of the in_features, this will be the srs for the out_feature_class
srs_id = arcpy.Describe(in_features).spatialReference.factoryCode
 
## this list will hold the names of the input fields in order
in_fld_names = [fld.name for fld in arcpy.ListFields(in_features) if fld.type != "OID"]
 
## we need the OID field to be able to create the ORIG_FID field in the output
oid_fld = [fld.name for fld in arcpy.ListFields(in_features) if fld.type=="OID"][0]
in_fld_names.insert(0, oid_fld)
 
## add field for accessing geometry
in_fld_names.append("SHAPE@")
 
## create a copy of the in_fld_name for the out_feature_class
out_fld_names = list(in_fld_names)
out_fld_names[0] = "ORIG_FID"

Create a temporary feature class and define schema

We will make use of the memory workspace and create a linear feature class using the input polygon feature class schema as a template and adding the ORIG_FID field.

				
					## create a temporary linear feature class in the memory workspace.
temp_fc = arcpy.management.CreateFeatureclass("memory", "temp_vertices", "POLYLINE",
    in_features, "SAME_AS_TEMPLATE", "SAME_AS_TEMPLATE", srs_id)
 
## add field for ORIG_FID
arcpy.management.AddField(temp_fc, "ORIG_FID", field_type="LONG", field_is_nullable="NULLABLE")

Insert records into memory feature class

Now we need to iterate through each polygon feature and convert the boundaries to polylines. If the input is a multipart polygon, the output is a multipart polyline. The attributes are maintained from the input to the output and we cater for the ORIG_FID.

				
					arcpy.SetProgressorLabel("Converting polygon boundaries to lines.")
 
## use a search cursor to iterate through the polygons
with arcpy.da.SearchCursor(in_features, in_fld_names) as s_cursor:
    ## use an insert cursor to insect the linear features into the temp_fc
    with arcpy.da.InsertCursor(temp_fc, out_fld_names) as i_cursor:
        ## for each record in the polygon feature class
        for row in s_cursor:
            ## get all attributes, less the geometry as a list
            row_attributes = list(row[0:-1])
 
            ## create a list to hold all polylines that make up the
            ## polygon boundary
            polyline_list = []
 
            ## for each port in the polygon geometry
            for index, part in enumerate(row[-1]):
                ## at the part to the polyline_lst
                polyline_list.append(row[-1].getPart(index))
 
            ## create an arcpy Array from the polyline_lst
            pl_array = arcpy.Array(polyline_list)
            ## append the Polyline to the attributes
            row_attributes.append(arcpy.Polyline(pl_array))
 
            ## insert the record, attributes and linear geometry to the temp_fc
            i_cursor.insertRow(row_attributes)
 
arcpy.SetProgressorLabel("Finished converting polygon boundaries")

Export to disk

We can now write our temporary feature class from the memory workspace to disk.

				
					arcpy.SetProgressorLabel("Writing output feature class")
 
## write the temp_fc to disk
arcpy.conversion.ExportFeatures(temp_fc, out_feature_class)

Cleanup the Memory Workspace

				
					## clean us the memory workspace
arcpy.Delete_management(temp_fc)

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Create the tool in ArcGIS Pro

Save your script and open up ArcGIS Pro. Right-click on your toolbox/toolset of choice and select New > Script. The New Script window will appear. In the General tab set Name to polygonToLine, Label to Polygon to Line (Basic), and the Description to Polygon to Line with a Basic License.

In the Parameters tab set as per below. Set the Filter for Input Features to Feature Type: Polygon, and Output Feature Class parameter Direction to Output and with a Filter of Feature Type: Polyline.

In the Execution tab, click the folder icon in the top-right corner and add your saved Python script.

Click OK and go test out the tool.

You can download the tool and other Advanced tools with a Basic license over on this page.

All the code in one place

You can find the entire code workflow below with links to important components in the documentation that were used.

				
					import arcpy
 
################################################################################
## Esri Documentation:
##  https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/polygon-to-line.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/functions/getparameterastext.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/functions/describe.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/functions/listfields.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/functions/setprogressorlabel.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/data-access/searchcursor-class.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/classes/array.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/classes/polyline.htm
##  https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/create-feature-class.htm
##  https://pro.arcgis.com/en/pro-app/latest/help/analysis/geoprocessing/basics/the-in-memory-workspace.htm
##  https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/add-field.htm
##  https://pro.arcgis.com/en/pro-app/latest/arcpy/data-access/insertcursor-class.htm
##  https://pro.arcgis.com/en/pro-app/latest/tool-reference/conversion/export-features.htm
##  https://pro.arcgis.com/en/pro-app/latest/tool-reference/data-management/delete.htm
##
## Syntax:
##     arcpy.management.PolygonToLine(in_features, out_feature_class, {neighbor_option})
##
## ArcGIS Pro Version: 3.1.0
##
################################################################################
 
################################################################################
## USER INPUTS #################################################################
 
## polygon featurer class to convert boundaries to lines
in_features = arcpy.GetParameterAsText(0)
 
## output feature class filepath
out_feature_class = arcpy.GetParameterAsText(1)
 
################################################################################
## TOOL OBJECT REQUIREMENTS ####################################################
 
## srs id of the in_features, this will be the srs for the out_feature_class
srs_id = arcpy.Describe(in_features).spatialReference.factoryCode
 
## this list will hold the names of the input fields in order
in_fld_names = [fld.name for fld in arcpy.ListFields(in_features) if fld.type != "OID"]
 
## we need the OID field to be able to create the ORIG_FID field in the output
oid_fld = [fld.name for fld in arcpy.ListFields(in_features) if fld.type=="OID"][0]
in_fld_names.insert(0, oid_fld)
 
## add field for accessing geometry
in_fld_names.append("SHAPE@")
 
## create a copy of the in_fld_name for the out_feature_class
out_fld_names = list(in_fld_names)
out_fld_names[0] = "ORIG_FID"
 
################################################################################
## CREATE OUPUT FEATURE CLASS ##################################################
 
## create a temporary linear feature class in the memory workspace.
temp_fc = arcpy.management.CreateFeatureclass("memory", "temp_vertices", "POLYLINE",
    in_features, "SAME_AS_TEMPLATE", "SAME_AS_TEMPLATE", srs_id)
 
## add field for ORIG_FID
arcpy.management.AddField(temp_fc, "ORIG_FID", field_type="LONG", field_is_nullable="NULLABLE")
 
################################################################################
## PROCESS POLYGONS TO LINES ###################################################
 
arcpy.SetProgressorLabel("Converting polygon boundaries to lines.")
 
## use a search cursor to iterate through the polygons
with arcpy.da.SearchCursor(in_features, in_fld_names) as s_cursor:
    ## use an insert cursor to insect the linear features into the temp_fc
    with arcpy.da.InsertCursor(temp_fc, out_fld_names) as i_cursor:
        ## for each record in the polygon feature class
        for row in s_cursor:
            ## get all attributes, less the geometry as a list
            row_attributes = list(row[0:-1])
 
            ## create a list to hold all polylines that make up the
            ## polygon boundary
            polyline_list = []
 
            ## for each port in the polygon geometry
            for index, part in enumerate(row[-1]):
                ## at the part to the polyline_lst
                polyline_list.append(row[-1].getPart(index))
 
            ## create an arcpy Array from the polyline_lst
            pl_array = arcpy.Array(polyline_list)
            ## append the Polyline to the attributes
            row_attributes.append(arcpy.Polyline(pl_array))
 
            ## insert the record, attributes and linear geometry to the temp_fc
            i_cursor.insertRow(row_attributes)
 
arcpy.SetProgressorLabel("Finished converting polygon boundaries")
 
################################################################################
## WRITE TO DISK ###############################################################
 
arcpy.SetProgressorLabel("Writing output feature class")
 
## write the temp_fc to disk
arcpy.conversion.ExportFeatures(temp_fc, out_feature_class)
 
################################################################################
## CLEAN UP ####################################################################
 
## clean us the memory workspace
arcpy.Delete_management(temp_fc)
 
################################################################################