topic polyline to polygon (comparison tool and own code) in Python Questions

polyline to polygon (comparison tool and own code)

SibghatUllah1 — Sun, 12 Dec 2021 05:29:22 GMT

I am trying to convert a ploy line feature class to polygon without using Arc info Advanced Licence.The code i am using runs fine and converts polyline to polygon. I have run the "tool feature to polygon" to make a comparison.My code is not converting all lines to polygon(See Screenshot).I have also attached my code.please guide me to get the same results.

Polyline :Red(to be converted)

Mycode:Brown

Feature to polygon: Blue

import arcpy

import arcpy
import os
from arcpy import env
env.overwriteOutput = True
starttime = time.time()
localtime = time.asctime( time.localtime(time.time()) )

# Create a value table that will hold the input feature classes for Merge

mxd=arcpy.mapping.MapDocument("CURRENT")
df = arcpy.mapping.ListDataFrames(mxd, "")[0]

for lyr in arcpy.mapping.ListLayers(mxd,"",df):
    if not lyr.isGroupLayer:
        arcpy.AddMessage(lyr.name)
        if "Export" in lyr.name :
            break

desc = arcpy.Describe(lyr)
shapefieldname = desc.ShapeFieldName
outPolys=r'C:\RAECGIStoCAD\test.gdb\temp'
arcpy.DeleteFeatures_management(r'C:\RAECGIStoCAD\test.gdb\temp')
joinoutput=r'C:\RAECGIStoCAD\test.gdb\join'
spatialRef = arcpy.Describe(lyr).spatialReference
featureList = []

#array = arcpy.Array()
cursor = arcpy.da.InsertCursor(outPolys, ['SHAPE@'])
rows = arcpy.SearchCursor(lyr)
for row in rows:
    # Create the geometry object
    feat = row.getValue(shapefieldname)
    #print "Feature %i: " % row.getValue(desc.OIDFieldName)
    partnum = 0
    part_list = []
    # Step through each part of the feature
    for part in feat:

        polygonArray = arcpy.Array()
        for pnt in feat.getPart(partnum):
            if pnt:
                # Add to list
                part_list.append([pnt.X, pnt.Y])
                polygonArray.add(arcpy.Point(pnt.X,pnt.Y))


                partnum += 1
    print partnum
    print part_list
    polygon = arcpy.Polygon(polygonArray)
    featureList.append(polygon)


    cursor.insertRow([polygon])
del cursor
endtime = time.time()
totaltime = endtime-starttime
print "\nScript took " + str(totaltime/60) + " minutes to run"

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Re: polyline to polygon (comparison tool and own code)

FC_Basson — Mon, 22 May 2017 07:59:17 GMT

I think your partnum counter on line 46 is indented one line too many.

Re: polyline to polygon (comparison tool and own code)

SibghatUllah1 — Mon, 22 May 2017 08:34:54 GMT

Dear FC Basson,

partnum counter i hv only placed to check the polygon (coordinates ) only.I want to know what logic is behind feature to polygon tool?

Re: polyline to polygon (comparison tool and own code)

JayantaPoddar — Mon, 22 May 2017 10:04:30 GMT

With an ArcGIS for Desktop Standard, you can use the Construct Polygons command on the Advanced Editing toolbar to create polygons from lines in ArcMap.

Also found a link How to create a polygon feature class from polylines in Python ArcGIS?

Re: polyline to polygon (comparison tool and own code)

SibghatUllah1 — Mon, 22 May 2017 10:13:00 GMT

Dear Jayanta,

I know about these tools.My main concern is about the result comparison. I want to know the logic behind feature to polygon tool?there is something missing in my code.

Re: polyline to polygon (comparison tool and own code)

FC_Basson — Mon, 22 May 2017 10:28:57 GMT

Yes, but you are incorrectly increasing the counter in the next indented for loop iterating the vertices and not in the part iteration. So you will always just process the first (index 0) part and skip the rest.

Re: polyline to polygon (comparison tool and own code)

SibghatUllah1 — Mon, 22 May 2017 10:55:53 GMT

Actually i just posted the code for creating polygon (i was using if statement ) and could not removed while posting.

I am displaying each polygon vertices and coordinates. The problem is that some line features have only two vertices (starting and ending) .My code is not converting them as it is not a polygon(we need at least three vertices).Please guide me to convert all lines as feature to polygon tool is converting.

import arcpy
import os
from arcpy import env
env.overwriteOutput = True
starttime = time.time()
localtime = time.asctime( time.localtime(time.time()) )

# Create a value table that will hold the input feature classes for Merge

mxd=arcpy.mapping.MapDocument("CURRENT")
df = arcpy.mapping.ListDataFrames(mxd, "")[0]

for lyr in arcpy.mapping.ListLayers(mxd,"",df):
if not lyr.isGroupLayer:
arcpy.AddMessage(lyr.name)
if "Export" in lyr.name :
break

desc = arcpy.Describe(lyr)
shapefieldname = desc.ShapeFieldName
outPolys=r'C:\RAECGIStoCAD\test.gdb\temp'
arcpy.DeleteFeatures_management(r'C:\RAECGIStoCAD\test.gdb\temp')
joinoutput=r'C:\RAECGIStoCAD\test.gdb\join'
spatialRef = arcpy.Describe(lyr).spatialReference
featureList = []

#array = arcpy.Array()
cursor = arcpy.da.InsertCursor(outPolys, ['SHAPE@'])
rows = arcpy.SearchCursor(lyr)
for row in rows:
# Create the geometry object
feat = row.getValue(shapefieldname)
#print "Feature %i: " % row.getValue(desc.OIDFieldName)
partnum = 0
part_list = []
# Step through each part of the feature
for part in feat:

polygonArray = arcpy.Array()
for pnt in feat.getPart(partnum):
if pnt:
# Add to list
part_list.append([pnt.X, pnt.Y])
polygonArray.add(arcpy.Point(pnt.X,pnt.Y))

partnum += 1
print partnum
print part_list
polygon = arcpy.Polygon(polygonArray)
featureList.append(polygon)

cursor.insertRow([polygon])
del cursor
endtime = time.time()
totaltime = endtime-starttime
print "\nScript took " + str(totaltime/60) + " minutes to run"

Re: polyline to polygon (comparison tool and own code)

FC_Basson — Mon, 22 May 2017 11:00:02 GMT

Could you please edit your post and use the Syntax Highlighter for your code? The indentation is cryptic as it currently is.

Re: polyline to polygon (comparison tool and own code)

SibghatUllah1 — Sun, 12 Dec 2021 05:29:25 GMT

import arcpy
import os
from arcpy import env
env.overwriteOutput = True
starttime = time.time()
localtime = time.asctime( time.localtime(time.time()) )

# Create a value table that will hold the input feature classes for Merge

mxd=arcpy.mapping.MapDocument("CURRENT")
df = arcpy.mapping.ListDataFrames(mxd, "")[0]

for lyr in arcpy.mapping.ListLayers(mxd,"",df):
    if not lyr.isGroupLayer:
        arcpy.AddMessage(lyr.name)
        if "Export" in lyr.name :
            break

desc = arcpy.Describe(lyr)
shapefieldname = desc.ShapeFieldName
outPolys=r'C:\RAECGIStoCAD\test.gdb\temp'
arcpy.DeleteFeatures_management(r'C:\RAECGIStoCAD\test.gdb\temp')
joinoutput=r'C:\RAECGIStoCAD\test.gdb\join'
spatialRef = arcpy.Describe(lyr).spatialReference
featureList = []

#array = arcpy.Array()
cursor = arcpy.da.InsertCursor(outPolys, ['SHAPE@'])
rows = arcpy.SearchCursor(lyr)
for row in rows:
    # Create the geometry object
    feat = row.getValue(shapefieldname)
    #print "Feature %i: " % row.getValue(desc.OIDFieldName)
    partnum = 0
    part_list = []
    # Step through each part of the feature
    for part in feat:

        polygonArray = arcpy.Array()
        for pnt in feat.getPart(partnum):
            if pnt:
                # Add to list
                part_list.append([pnt.X, pnt.Y])
                polygonArray.add(arcpy.Point(pnt.X,pnt.Y))


                partnum += 1
    print partnum
    print part_list
    polygon = arcpy.Polygon(polygonArray)
    featureList.append(polygon)


    cursor.insertRow([polygon])
del cursor
endtime = time.time()
totaltime = endtime-starttime
print "\nScript took " + str(totaltime/60) + " minutes to run"

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Re: polyline to polygon (comparison tool and own code)

LukeWebb — Mon, 22 May 2017 12:01:33 GMT

Put Simply, feature to polygon considers ALL INPUT FEATURES when creating shapes, and is a more complicated totally different algorithm than what you have begun to implement with your "Feature by Feature" code.

You could look to dissolve the input lines, and then explode, as a pre-process, and then rewrite your own algorithym, but its probably a little complex to get good results!

Re: polyline to polygon (comparison tool and own code)

SibghatUllah1 — Mon, 22 May 2017 13:49:31 GMT

Dear Luke,

Actually my client dont have advanced license.yes i was storing only vertices coordinates and drawing a new polygon. Is it possible to construct polygon using python script? any suggestion

https://community.esri.com/external-link.jspa?url=http%3A%2F%2Fdesktop.arcgis.com%2Fen%2Farcmap%2F10.3%2Fmanage-data%2Fcrea…

Re: polyline to polygon (comparison tool and own code)

LukeWebb — Tue, 06 Jun 2017 16:40:34 GMT

I am unable to come up with a decent algorithym.... and I love a challenge!

I feel ESRI have constructed a decent tool, and knowing this, put it behind an advanced license for 'commercial' reasons I would advise looking at the open source tools provided in our other threads, as this is a not a simple task to accomplish.

Unless you have any good ideas of how the algorithm should work I could try to implement