topic Re: Creating polyline from text file in Python Questions

Creating polyline from text file

KennethKirkeby — Fri, 10 Dec 2021 22:08:46 GMT

So I need to create a line based on a series of points. In the example below, there are 4 lines to be created, Line_1. Line_2, etc. Struggling with the loop that creates each pointList.

cursor = arcpy.da.InsertCursor(fc, ["Name","SHAPE@"])
   
for ln in inputFile:
  name = ln[0]
  pointList = Point. Array() # initial Array
    ln = line.split(",") # Split the lines in text file
    point = arcpy.Point(ln[1], ln[2]) # Create points 
    pointList.add(point) # Add points to array
        polyline = arcpy.Polyline(pointList)
cursor.insertRow(name, polyline)

Line_1, 529018.125025, 4108038.05548 Line_1, 529005.718792, 4108028.20659 Line_1, 528993.340503, 4108018.73931 Line_1, 528980.990158, 4108009.65364 Line_1, 528968.667757, 4108000.94958 Line_2, 528956.373301, 4107992.62713 Line_2, 528944.106788, 4107984.68629 Line_2, 528931.86822, 4107977.12705 Line_3, 528919.657595, 4107969.94943 Line_3, 528907.474915, 4107963.15341 Line_3, 528895.320179, 4107956.739 Line_3, 528883.193387, 4107950.7062 Line_4, 528871.09454, 4107945.055 Line_4, 528859.023636, 4107939.78542 Line_4, 528846.980676, 4107934.89744 Line_4, 528834.965661, 4107930.39107

Re: Creating polyline from text file

DarrenWiens2 — Fri, 12 Feb 2016 19:50:54 GMT

Please post your entire script with code formatting.

Posting Code blocks in the new GeoNet

edit: you reference ln[0] before creating the ln variable.

edit 2: not sure what this line means: Pointillist = occupies. Array () # initial Array

Should probably be: pointList = arcpy.Array()

edit 3: your variable names need to match exactly. Pointllist <> pointList

Re: Creating polyline from text file

KennethKirkeby — Fri, 12 Feb 2016 20:17:35 GMT

Corrected code and formatting, I hope.

Re: Creating polyline from text file

DanPatterson_Retired — Fri, 12 Feb 2016 20:22:58 GMT

your polyline line 09 needs to be completely dedented

Re: Creating polyline from text file

KennethKirkeby — Fri, 10 Dec 2021 22:08:49 GMT

for ln in inputFile:  
    pointList = arcpy.Array()
    ln = ln.split(",")
    name = ln[0]
    point = arcpy.Point(ln[1], ln[2])
    pointList.add(point)  
polyline = arcpy.Polyline(pointList)

Re: Creating polyline from text file

DanPatterson_Retired — Fri, 12 Feb 2016 20:46:08 GMT

Kenneth...

nice dedent...

Now work with us...

What did it print out?

I bet you thought it would print out the coordinates...assuming it worked at all?

Did you get an error?

Anything else to add?

Re: Creating polyline from text file

DarrenWiens2 — Fri, 12 Feb 2016 20:54:05 GMT

Check out the example on the Polyline help page, paying particular attention to fact that multiple lines require multiple lists, or rather, a list of lists.

Re: Creating polyline from text file

KennethKirkeby — Fri, 10 Dec 2021 22:08:51 GMT

forln in inputFile: 
    pointList = arcpy.Array()
    ln = ln.split(",")
    name = ln[0]
    point = arcpy.Point(ln[1], ln[2])
    pointList.add(point) 
polyline = arcpy.Polyline(pointList)
cursor.insertRow((name, polyline))

Attribute table:

Shape Name

polyline Line_4

Re: Creating polyline from text file

DarrenWiens2 — Fri, 12 Feb 2016 21:00:18 GMT

pointList is getting wiped out for each line in your input file. Within each iteration, you need to add the contents of pointList to an overarching list to persist the coordinates until you are ready to create the lines.

Re: Creating polyline from text file

KennethKirkeby — Fri, 12 Feb 2016 21:01:57 GMT

@Aaron - That's what I'm having trouble doing if I understand your point. Create a set of points for Line_1, then Line_2, etc. That's what I do not know how to do.

Re: Creating polyline from text file

DarrenWiens2 — Fri, 10 Dec 2021 22:08:54 GMT

This will probably take some digesting:

>>> import csv
... fc = "myLines"
... with open('C:/junk/points.csv', 'rb') as csvFile:
...     reader = csv.reader(csvFile)
...     dict = {}
...     for row in reader:
...         dict.setdefault(row[0],arcpy.Array()).add(arcpy.Point(row[1],row[2]))
... print dict
... cursor = arcpy.da.InsertCursor(fc, ["Name","SHAPE@"])
... for k,v in dict.iteritems():
...     cursor.insertRow([k,arcpy.Polyline(v)])
...     
{'Line_1': <Array [<Point (529018.125025, 4108038.05548, #, #)>, <Point (529005.718792, 4108028.20659, #, #)>, <Point (528993.340503, 4108018.73931, #, #)>, <Point (528980.990158, 4108009.65364, #, #)>, <Point (528968.667757, 4108000.94958, #, #)>]>, 'Line_3': <Array [<Point (528919.657595, 4107969.94943, #, #)>, <Point (528907.474915, 4107963.15341, #, #)>, <Point (528895.320179, 4107956.739, #, #)>, <Point (528883.193387, 4107950.7062, #, #)>]>, 'Line_2': <Array [<Point (528956.373301, 4107992.62713, #, #)>, <Point (528944.106788, 4107984.68629, #, #)>, <Point (528931.86822, 4107977.12705, #, #)>]>, 'Line_4': <Array [<Point (528871.09454, 4107945.055, #, #)>, <Point (528859.023636, 4107939.78542, #, #)>, <Point (528846.980676, 4107934.89744, #, #)>, <Point (528834.965661, 4107930.39107, #, #)>]>}

I saved your sample data to a csv file. Then, for each row in the csv, add the coordinates (point objects within an array object) to a dictionary, according to the line ID. Once the dictionary is created, for each line ID in the dictionary, insert a feature into the feature class, passing name and shape.

Re: Creating polyline from text file

KennethKirkeby — Sat, 13 Feb 2016 02:55:23 GMT

The print was just a way to know when it ended. I did get it to update my shapefile but with only the last line of the loop.

Re: Creating polyline from text file

DanPatterson_Retired — Sat, 13 Feb 2016 03:09:01 GMT

logic with indentation (since this is still homework I presume)

make an empty point list (array)

read the file line by line:

split the line, and get the point oordinates

make the point

add the point to the point array

Re: Creating polyline from text file

XanderBakker — Fri, 10 Dec 2021 22:08:57 GMT

Darren Wiens shows a very clean piece of code to do what you are after. I would definitely go for the solution provided by Darren.

If you would have continued along the lines of what you where doing, you would probably end up with something like the code below. Just for you to understand what was missing in your initial code.

import arcpy

fc = r'D:\Xander\GeoNet\TXT2Polyline\test.gdb\myFeatureClass'
txt_file = r'D:\Xander\GeoNet\TXT2Polyline\myTextFiles.txt'

with arcpy.da.InsertCursor(fc, ["Name","SHAPE@"]) as cursor:
    with open(txt_file, 'r') as inputFile:
        prev_name = None
        pointList = arcpy.Array()
        for line in inputFile:
            ln = line.split(",")
            name = ln[0]
            point = arcpy.Point(float(ln[1]), float(ln[2]))
            if name != prev_name:
                # start of a new line
                if pointList.count > 1:
                    # if previous list has more than 2 points, write line
                    polyline = arcpy.Polyline(pointList)
                    cursor.insertRow((prev_name, polyline, ))
                # create a new array and add current point
                pointList = arcpy.Array()
                pointList.add(point)
            else:
                # same name as previous name, add point to current list
                pointList.add(point)
            prev_name = name

        # add last line
        polyline = arcpy.Polyline(pointList)
        cursor.insertRow((name, polyline, ))

Re: Creating polyline from text file

KennethKirkeby — Tue, 16 Feb 2016 14:47:57 GMT

This is what I was trying to do for my script. For whatever reason, I could not get the looping straight.Thanks so much for the assistance.

Re: Creating polyline from text file

XanderBakker — Tue, 16 Feb 2016 17:08:36 GMT

Could you mark the answer provided by Darren as the "Correct Answer"? I think it provides the best solution to your question.

Re: Creating polyline from text file

XanderBakker — Wed, 17 Feb 2016 00:11:30 GMT

Hi Kenneth Kirkeby , I would really like to ask you to mark the post by Darren as the correct answer. Apart from being the first to provide a solution, the solution really shows a cleaner, better and shorter way to solve this problem. By marking his better solution as the correct answer you will enable other users to find his answer more easily.

Thanks, Xander

Re: Creating polyline from text file

DanPatterson_Retired — Wed, 17 Feb 2016 00:14:06 GMT

Fixed...