Insert cursor for first row in unique value set arcpy

Question

I really need some guidance on how to create a python script with arcpy to:

1) Search through a table for unique values in a field.

2) For the first row in each unique valueset, insert that row into a new empty table.

I have been trying to get this work with the da.SearchCursor and da.InsertCursor, but can't really get 2) to work..

The reason why I want to do this is that I have a table with two fields; "wellbore_name" is the ID for wells, "Units" are concatenated geological units for the specific well. There are several rows for each unique ID, and I want an output table with as many rows as unique IDs. Since the units are concatenated I only need one row for each ID.

This is probably easy for someone fluent in cursors, but alas I am not. Hopefully someone out there can help me with this :-)

Answer 1

I would take a different approach and use Delete Identical (Data Management). The following script creates a copy of your table or FC and then removes the duplicate rows in that copy.

import arcpy

table = r'C:\test\temp.gdb\table'
copy = r'C:\test\temp.gdb\table2'

# Create a copy of your table
arcpy.CopyFeatures_management(table, copy)

# Delete duplicate rows based on the field "test"
arcpy.DeleteIdentical_management(copy, "test")

Answer 2

Vamping on PolyGeo's comment, I believe that the Summary Statistics tool would work easily. If I understand correctly you just need a list of unique values for the "Units" field. You can set up the tool like this (see the screenshot) except instead of using the "Name" field, you would use "Units". [Be sure to add Wellbore_Name w/ stat type "FIRST" as one of your statistics fields.] You will get a red error circle until you choose the statistic type. I think "FIRST" would be correct here.

Aaron's comment is correct so I updated the screenshot. You actually need to use the "Units" as the case field and use the Wellbore_Name with statistic type set to First. This is also just going to give you a table not your feature class (which is probably what you want anyway).

Answer 3

As mentioned by several other users here. Using Search and Insert cursors may not be necessary, but if for some reason you would still like to see how it is done, the following script should do everything you need. You will need to setup parameters for the script tool. I'll assume for now that you already know how to do this.

Parameters:

1. (0) Input Features - Feature Class
2. (1) Output Location - Workspace
3. (2) Output Name - String

Updated Script:

import arcpy, os
from arcpy import env

arcpy.env.overwriteOutputs = True

inFC = arcpy.GetParameterAsText(0)
outLoc = arcpy.GetParameterAsText(1)
outName = arcpy.GetParameterAsText(2)

fieldList = ["WELLBORE_NAME", "Units"]

desc = arcpy.Describe(inFC)
geoType = desc.shapeType.upper()
spatRef = arcpy.Describe(inFC).spatialReference

arcpy.CreateTable_management(outLoc, str(outName), inFC)  

newFeature = os.path.join(outLoc, str(outName))

dataArray = []

insertCursor = arcpy.da.InsertCursor(newFeature, (fieldList))

with arcpy.da.SearchCursor(inFC, (fieldList)) as cursor:
    for row in cursor:
        if (row[0] not in dataArray):                          
            dataArray.append(row[0])
            insertCursor.insertRow((row[0], row[1]))


    del row
del cursor

This could be customized to meet the needs of other datasets by adding the appropriate fields and row references.

Answer 4

1) Create uniq list of values with python set

uniq = set() name_field = "test_field" with arcpy.da.SearchCursor(your_table, [name_field]) as sCur: for row in Scur: set.add(row[0])

2) For uniq values find first id (using OID@ token to access id value of row):

for uniq_value in uniq: with arcpy.da.SearchCursor(your_table, [name_field,"OID@"])as sCur: # select min value of id for each uniq value print min([row[1] for row in sCur if row[0]==uniq_value])

In block 2 you can paste InsertCursor for adding this values to new table. If you need geometry in out table, you can access geometry with token "SHAPE@" and paste it in InsertCursor too.