topic Python Accumulate Values in Python Questions

Python Accumulate Values

ToddHenry1 — Tue, 15 Sep 2015 11:44:08 GMT

In another post, I found this python script that creates a running total. I was able to modify it to do a running product, but I need to have the running product reset when the value of another field changes.

How might I modify this code to do that?

Calculate the accumulative value of a numeric field.
Expression:
accumulate(!FieldA!)
Expression Type:
PYTHON_9.3
Code Block:
total = 0
def accumulate(increment):
global total
if total:
total *= increment
else:
total = increment
return total

My data is similar to this

ID	Value
1
1	9
2
2	5

The answer would be 1 = 81 and 2 = 25 in the 2nd row of each ID.

Re: Python Accumulate Values

FreddieGibson — Tue, 15 Sep 2015 14:27:08 GMT

Have you tried adding another global variable to store the value in the other field so that you can check to see if it changed? You'd also need to add another variable to the expression to pass in the id value.

Re: Python Accumulate Values

ToddHenry1 — Wed, 23 Sep 2015 21:43:01 GMT

Below is the code I ended up using with some help from Tech Support.

This goes in the code block:

total = 0

LocationID = 0

def accumulate(locID, Inc):

global total, LocationID

if locID != LocationID:

total = 0

LocationID = locID

if total: total = total*Inc

else: total = Inc

return total

In the expression I use accumulate(!LocationID!,!IncField!)

The LocationID is my grouping Field and the IncField is the one that gets multiplied together.

Re: Python Accumulate Values

DanPatterson_Retired — Wed, 23 Sep 2015 22:04:35 GMT

Just like Freddie said ... for others following this

total

LocationID

in the posted solution are both global variables whose values get updated inside the scope of the def . Globals...although generally not recommended... are useful should you need to persist an initial value so that it can be updated as the cursor is incremented