topic Re: Creating multiple fields with ranks using arcpy in Python Questions

Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Sat, 11 Dec 2021 23:33:34 GMT

I have a field named "arrondissement" (district), which contains as attributes integers from 1 to 20. My task is to create a column for each arrondissement with the ranks (short integers) relative to the shape area for the connecting areas to voting stations of the same district.

I hope it makes sense, not really sure how to do it to be honest I'm lost at the moment. Besides adding a field, perhaps multiple ones with a loop by using ListFields and AddField, I don't really know what else to do.

EDIT:

While figuring out what I have to do, practically creating a field for each arrondise, and in each, rank each FID (which are part of the respective arrondise) by the size of its shape area.

import arcpy

arcpy.env.workspace = "D:/M1 Geomatique/Programmation II/Dossier"

fc = "zones_rattachement.shp"

try:
    fieldRoot = "RANG_R"
    for counter in range(1,21):
        arcpy.AddField_management(fc, fieldRoot + str(counter),'SHORT')

    
    size_rank = 1
    numlist = list(range(1,21))
    for num in numlist:
        arcpy.SelectLayerByAttribute_management(fc, "NEW_SELECTION", "arrondisse = '%c'")
        rows = arcpy.UpdateCursor(fc, sort_fields="shape_area D")
        for row in rows:
            row.setValue("RANG_R1", size_rank)
            size_rank += 1
            rows.updateRow(row)

            
except:
    arcpy.GetMessages()

Message was edited by: Florin-Daniel Cioloboc

Re: Creating multiple fields with ranks using arcpy

JeffWard — Sat, 11 Dec 2021 23:33:37 GMT

How about

import arcpy

fc = 'yourFeatureClass' #insert your feature class here
fieldRoot = 'RANK' #root name of the field
for counter in range(1,20):
    arcpy.AddField_management(fc, fieldRoot + str(counter), 'LONG')

Re: Creating multiple fields with ranks using arcpy

JamesCrandall — Wed, 29 Apr 2015 15:42:09 GMT

Ranking field values | ArcPy Café

Re: Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Sat, 11 Dec 2021 23:33:40 GMT

From what I can read, it should create 20 columns with a different name, not sure why in my case it's not working.

import arcpy

arcpy.env.workspace = "D:/M1 Geomatique/Programmation II/Dossier"

fc = "zones-de-rattachement-des-bureaux-de-vote-en-2014"

try:
    fieldRoot = "RANG_RAPPORT"
    for counter in range(1,20):
        arcpy.AddField_management(fc, fieldRoot + str(counter),'LONG')

except:
    arcpy.GetMessages()

Re: Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Wed, 29 Apr 2015 18:34:34 GMT

Interesting solution, I think I ran into it yesterday but if:

Note: dBase (and shapefiles) does not support ORDER BY as used above by arcpy.da.UpdateCursor’s sql_clause argument.

is it possible, how to go around it, what can substitute the SQL clause? I guess, sorted() would work?

Re: Creating multiple fields with ranks using arcpy

JeffWard — Wed, 29 Apr 2015 19:08:43 GMT

What type of data are you working with? That is a very long feature class name, and I tend to avoid dashes in my feature class names because it has caused me problems in the past.

If you are using a file geodatabase doesn't your workspace variable need to have the .gdb extension?

arcpy.env.workspace = "D:/M1 Geomatique/Programmation II/Dossier.gdb"

Or if you are working with a shapefile you are missing the .shp extension in your fc variable and the field name is probably too long.

Re: Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Wed, 29 Apr 2015 21:02:14 GMT

I'm working with a shapefile, not with a geodatabase, in that case, I omitted the .shp extension.

Re: Creating multiple fields with ranks using arcpy

JeffWard — Sat, 11 Dec 2021 23:33:42 GMT

Then you will need to add .shp to the end of your feature class name.

fc = "zones-de-rattachement-des-bureaux-de-vote-en-2014.shp"

Also, your field name is too long, they need to be 10 or fewer. Since you are going to be tacking on up to two characters to the end, you will need to have a field name 8 characters or fewer.

Re: Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Thu, 30 Apr 2015 06:36:18 GMT

Done, it worked, now I have a script that actually creates 20 fields. I've also modified the name of .shp, as it was just too long.

Re: Creating multiple fields with ranks using arcpy

deleted-user-3rTxRfVTcNm- — Thu, 30 Apr 2015 07:14:02 GMT

Trying to rank rows which are part of a certain arrondise, in terms of size of shape_area. To increase visibility I updated the first post.

Re: Creating multiple fields with ranks using arcpy

JamesCrandall — Thu, 30 Apr 2015 14:23:04 GMT

Then don't use shapefiles. It's pretty simple to migrate your data to a File Geodatabase, a scratch workspace, or I'd even consider just adding the source data you intend to process to in_memory feature class if possible. You won't have to deal with shapefile limitations.