topic Re: Update Field from Multiple Field(s) in Python Questions

Update Field from Multiple Field(s)

ModernElectric — Mon, 19 Sep 2016 18:00:30 GMT

I have been looking around the internet all morning to figure out how to write a Python script to accomplish what I need to do, and so far, I am not finding what I need. Need to see if someone can start me in the correct direction.

I have (2) text fields:

ACALARA TYPE and ACALARA MODEL with coded meter type attributes

Another field:

ACALARA METER TYPE will hold the actual Meter Type

The data in the first two fields is held in a different database and I have a Python script built that will take that data and update these Feature Class Fields.

What I need to do is build a second python script that is composed of an if/else statement.

EXAMPLE:

If ACALARA TYPE = 75 and ACALARA MODEL = 130

Then the ACALARA METER TYPE field will update to show "CEN3S4S20"

If ACALARA TYPE = 109 and ACALARA MODEL = 2

Then the ACALARA METER TYPE field will update to show "UMT2.1"

There are around 2 dozen other combinations with additional Meter Type outputs that I will have to include

Figuring out how to write this code will help with other Feature Classes that I have been updating manually.

Thank You

Re: Update Field from Multiple Field(s)

curtvprice — Sun, 12 Dec 2021 01:09:02 GMT

You can do this with the Calculate Field tool with a code block. I highly recommend using Python for many reasons.

Expression

proc(!ACALARA_TYPE!, !ACALARA_MODEL!)‍‍

Code block

def proc(actype, acmodel):
    # try except block handles non-handled cases!
    try:
        if actype == 75 and acmodel == 130:
            result = "CEN3S4S20"
        elif actype == 109 and acmodel == 2:
            result = "UMT2.1"
        else:
            # we ran into an uncovered case
            raise(Exception)
    except:
        result = "undefined"
    return result‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Update Field from Multiple Field(s)

ModernElectric — Mon, 19 Sep 2016 18:36:43 GMT

Curtis:

Thank you for the reply and the script. I tried entering it into Calculate field through the FC Table. However, all of the fields in the ACALARA METER TYPE field got filled in with "undefined" from the last part of the script.

Re: Update Field from Multiple Field(s)

ModernElectric — Mon, 19 Sep 2016 18:46:11 GMT

I know there is a way to run this process through Arcpy Update Cursor. However, I am not sure exactly how to start the code.

Re: Update Field from Multiple Field(s)

curtvprice — Sun, 12 Dec 2021 01:09:04 GMT

There is probably an issue with your code (or mine); any error in your code will give you "undefined" because I'm trapping all exceptions.

Until you get it working on one, set up except block to do this, then you'll get an error message.

    except:
        raise ## remove this line after you get it working
        result = "undefined"
    return result‍‍‍‍‍‍‍‍‍‍‍‍

Re: Update Field from Multiple Field(s)

curtvprice — Sun, 12 Dec 2021 01:09:07 GMT

If you are really using spaces in your field names, I highly recommend not doing so. https://community.esri.com/people/curtvprice/blog/2016/05/07/how-to-name-things-in-arcgis?sr=search&searchId=8e90d673-8df0-4fc8-a197-51e964eb6f5b&searchIndex=0

In the python window, or in a script you can do this, it will run on the selected features in your layer or table view (as does Calculate Field):

UPDATE - fixed my exception handling - it was broken.

def proc(actype, acmodel):
    # try except block handles non-handled cases!
    try:
        if actype == 75 and acmodel == 130:
            result = "CEN3S4S20"
        elif actype == 109 and acmodel == 2:
            result = "UMT2.1"
        else:
            # we ran into an uncovered case
            raise Exception("Unhandled case: proc({}, {})".format(actype, acmodel))
    except Exception as msg:
        raise Exception(msg)  ## remove this line after you get it working
        result = "undefined"
    return result

flds = ["ACALARA_TYPE", "ACALARA_MODEL", "ACALARA_METER_TYPE"]
with arcpy.da.updateCursor("mylayer", flds) as rows:
    for row in rows:
        row[2] = proc(row[0], row[1])
        rows.updateRow(row)

‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Re: Update Field from Multiple Field(s)

DarrenWiens2 — Mon, 19 Sep 2016 19:58:19 GMT

I'm not 100% clear on the rules, but some of the lines in the solution above have a 3-space indent, while others have 4. I believe that once you establish a 4-space indent, you need to continue with that.

Re: Update Field from Multiple Field(s)

curtvprice — Mon, 19 Sep 2016 21:05:12 GMT

You sure do. I think I'm having trouble with the new highlight tool. I will do it an IDE window and paste in.

Re: Update Field from Multiple Field(s)

ModernElectric — Sun, 12 Dec 2021 01:09:10 GMT

Today is not my day apparently. I am running this through IDLE/Command Prompt I keep getting a runtime error. This is the code I have for the UpdateCursor. Maybe something is wrong??

fc = "C:\MEWCo GIS System\Electric System\MEWCo_Electric_Model-LOCAL.gdb\Secondary\SERVICE_LOCATION"
fields = ["ACALARA_TYPE", "ACALARA_MODEL", "ACALARA_METER_TYPE"]
 
def proc(actype, acmodel):
    # try except block handles non-handled cases!
    try:
        if actype == 75 and acmodel == 130:
            result = "CEN3S4S20"
        elif actype == 109 and acmodel == 2:
            result = "UMT2.1"
        else:
            # we ran into an uncovered case
            raise(Exception)
    except:
        raise  ## remove this line after you get it working
        result = "undefined"
    return result

with arcpy.da.UpdateCursor(fc, fields) as rows:
    for row in rows:
        row[2] = proc(row[0], row[1])
        rows.updateRow(row)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

Thank You

Re: Update Field from Multiple Field(s)

DarrenWiens2 — Mon, 19 Sep 2016 22:09:50 GMT

What is the exact runtime error?

Also, may not be the issue, but beware the way you're writing paths. You should use raw notation or other valid path syntax to avoid escape characters.

For example:

fc = r"C:\MEWCo GIS System\Electric System\MEWCo_Electric_Model-LOCAL.gdb\Secondary\SERVICE_LOCATION"

Re: Update Field from Multiple Field(s)

ModernElectric — Mon, 19 Sep 2016 22:14:45 GMT

The I get: "RuntimeError: Unspecific error"

Says something about line 20

Does the code and everything look okay? I added your suggestion and nothing.

Re: Update Field from Multiple Field(s)

DanPatterson_Retired — Tue, 20 Sep 2016 02:05:33 GMT

start by fixing the first line an putting the 'fc' variable into raw format as Darren notes. And on a side note, if you continue to use folders and filenames with spaces and other characters ... like dashes - ... you will continue to have problems.

'Says something about line 20' .... write it down, screen grab it, but at least report it. Error messages noted for a particular line are often the result of errors further on up the script, like the file name, because line 20 expects to use 'rows' but if the filename or fields are no good, the erro cascade begins.

Re: Update Field from Multiple Field(s)

curtvprice — Thu, 22 Sep 2016 21:15:42 GMT

Line 20 is where you call my function. This function seems to be working correctly though.

>>> proc(75, 130)
'CEN3S4S20'
>>> proc(109, 2)
'UMT2.1'

>> proc(109,4)
Runtime error
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "<string>", line 10, in proc
Exception

Note, my code is assuming the actype and acmodel fields are numeric and your output field is string.

I will update the code to more gracefully handle unhandled combinations, there is a syntax error in my raise statement.

UPDATE: after my fix:

>>> proc(109,4)
Runtime error
Traceback (most recent call last):
File "<string>", line 1, in <module>
File "<string>", line 12, in proc
Exception: Unhandled case: proc(109, 4)
>>>