topic Re: Python loop script to calculate cumulative sum based on another attribute being the same in Python Questions

Python loop script to calculate cumulative sum based on another attribute being the same

ClintonCooper1 — Mon, 21 Mar 2016 15:44:21 GMT

I am looking for a script that will calculate the cumulative sum of say population (based on a presorted table that I have created) as long as the variable of ID is the same. So it might look like

ID	POP	CUMPOP
1	100	100
1	250	350
1	150	500
2	100	100
2	500	600
3	150	150
3	600	750
3	100	850
3	150	1000

this:

Re: Python loop script to calculate cumulative sum based on another attribute being the same

WesMiller — Mon, 21 Mar 2016 16:11:31 GMT

Try the Dissolve—Help | ArcGIS for Desktop tool. You could dissolve based on ID and sum on either or both of your pop fields

Re: Python loop script to calculate cumulative sum based on another attribute being the same

JakeSkinner — Sun, 12 Dec 2021 02:47:57 GMT

Hi Clinton,

Try the following:

import arcpy
from arcpy import env
env.workspace = r"E:\Temp\Python\test.gdb"

table = "Sample"

list = []

#append IDs to list
with arcpy.da.SearchCursor(table, ["ID"]) as cursor:
    for row in cursor:
        list.append(row[0])

del cursor

#remove duplicates
list = set(list)

#update CUMPOP field
for id in list:
    with arcpy.da.UpdateCursor(table, ["POP", "CUMPOP"], "ID = {0}".format(id)) as cursor:
        firstTime = True
        for row in cursor:            
            if firstTime:
                row[1] = row[0]
                cursor.updateRow(row)
                newVal = row[0]
                firstTime = False
            else:
                print newVal
                row[1] = row[0] + newVal
                cursor.updateRow(row)
                newVal = row[0]

del cursor

Re: Python loop script to calculate cumulative sum based on another attribute being the same

ClintonCooper1 — Mon, 21 Mar 2016 16:32:35 GMT

Well I need the running cumulative average. After I run this loop, I need to be able to remove or select all the rows with a value greater than or less than a certain value that I choose for my analysis.

Re: Python loop script to calculate cumulative sum based on another attribute being the same

ClintonCooper1 — Mon, 21 Mar 2016 16:45:45 GMT

Thank you, this works perfectly!!

Re: Python loop script to calculate cumulative sum based on another attribute being the same

ClintonCooper1 — Mon, 21 Mar 2016 17:10:09 GMT

just for reference, I found one issue in line 33:

newVal = row[0]

Should be:

newVal = row[1]