I am new to python, and have not successfully coded an Update Cursor. I am unable to understand the documentation.

I have a geodatabase table of wells that i have built using python. I now want to loop through each row and update a field. the table contains a field called 'MD' which is type double and contains a depth value. I need to look at a second field called 'FM_Name' for two text strings that indicate the TOP and BOTTOM of a certain perforation zone. So, the cursor would loop though the rows which are sorted in ascending order, and update 'FM_Name' field with the word "Perf" in between the TOP and BOTTOM for each well.

This table has over 50K records, representing roughly 300 wells, so i really dont want to do this by hand.

Here is the table


This code should do the work you need to get done. Make sure the table is sorted as you expect. There is a GP tool Sort that can do that for you.

import arcpy
fc = r'C:\ArcGIS\Default.gdb\wells'

with arcpy.da.UpdateCursor(fc,['MD','FM_Name']) as upd_cur:
    for row in upd_cur: #start iterating rows in the table
        if row[1] == 'TOP': #if the FM_NAME column is 'TOP', then:
            row = upd_cur.next() #take next row in the table
            while row[1] != 'BOTTOM': #if the FM_NAME column is not 'BOTTOM', then:
                row[1] = 'PERF' #set the FM_NAME column to be 'PERF'
                upd_cur.updateRow(row) #update the row (writing changes)
                row = upd_cur.next() #take next row and jump back to the 'while' line

I have made some comments in the code so you will be able to catch up.

The results in the attribute table in ArcMap:

enter image description here

| improve this answer | |
  • 2
    @CaseyP., no problem at all! This scenario is somewhat more difficult to code comparing to a plain "all rows" update. Take your time to learn arcpy. Btw, there is a great list of resources for this - gis.stackexchange.com/questions/53816/…. – Alex Tereshenkov Sep 16 '16 at 15:55
  • I will certainly check those links out. thank you for your time and help! – Casey P. Sep 16 '16 at 18:05

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