Sum rasters failing with "Unexpected error"

ChrissyWhite — Tue, 27 Mar 2018 17:00:34 GMT

Hi, I am very new to python and am coming across an issue that I haven't been able to work out on my own.

I have 9 rasters that I need to sum. Nothing fancy, just a simple sum. I have this code that I used in another script (found on some blog somewhere) and it worked without any issue whatsoever:

rasters = arcpy.ListRasters('cf_*')

    i = 0
    for ras in rasters:
        if i == 0:
            sumras = arcpy.Raster(ras)
            i += 1
        else:
            sumras = sumras + ras
            i += 1
    sumras.save(outRasterCFS)

However, in my current script it fails with:

Traceback (most recent call last):
File "<module1>", line 32, in <module>
File "<module1>", line 25, in Cut
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Functions.py", line 4329, in Plus
    in_raster_or_constant2)
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Utils.py", line 53, in swapper
    result = wrapper(*args, **kwargs)
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Functions.py", line 4326, in Wrapper
    ["Plus", in_raster_or_constant1, in_raster_or_constant2])
RuntimeError: ERROR 999998: Unexpected Error.

When researching how to resolve this, I found another post somewhere that suggested cellstatistics might be better, so:

sumras = CellStatistics(rasters,"SUM","DATA")
sumras.save(outRasterCFS)

But it fails with:

Traceback (most recent call last):
File "<module1>", line 32, in <module>
File "<module1>", line 16, in Cut
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Functions.py", line 3149, in CellStatistics
    ignore_nodata)
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Utils.py", line 53, in swapper
    result = wrapper(*args, **kwargs)
File "C:\Program Files (x86)\ArcGIS\Desktop10.5\ArcPy\arcpy\sa\Functions.py", line 3145, in Wrapper
    [function] + Utils.flattenLists(in_rasters_or_constants))
RuntimeError: ERROR 999998: Unexpected Error.

Usually, when I run into problems that aren't very clear, I run it manually from ArcMap and can usually figure out what is going wrong in my python, but when I run CellStatistics from ArcMap, it fails as well:

ERROR 010092: Invalid output extent.

I really have no idea where to go from here. I can't find anything online that points me in a helpful direction...

Any thoughts or suggestions? I would greatly appreciate it!

Here is the entire script:

#Set environment
import arcpy
from arcpy import env
from arcpy.sa import *
wrkpath = r'E:\GIS_Data\GEO5419\MyWork'
arcpy.env.workspace = wrkpath
arcpy.env.overwriteOutput = True

def Cut():
    arcpy.CheckOutExtension("Spatial")
    topRaster = 'Site_DEM'
    outRasterCFS = wrkpath+'\CFSum'
    rasters = arcpy.ListRasters('cf_*')

sumras = CellStatistics(rasters,"SUM","DATA")
sumras.save(outRasterCFS)

##    i = 0
##    for ras in rasters:
##        if i == 0:
##            sumras = arcpy.Raster(ras)
##            i += 1
##        else:
##            sumras = sumras + ras
##            i += 1
##    sumras.save(outRasterCFS)

arcpy.CheckInExtension("Spatial")

if __name__ == '__main__':
Cut()

Re: Sum rasters failing with "Unexpected error"

ChrissyWhite — Tue, 27 Mar 2018 18:02:41 GMT

I figured it out not long after posting this. I wanted to delete this entire thread, but I cannot find an option to do so.

So, until I do, for anyone else having the same issue, the resolution was to add this to my code:

arcpy.env.extent = "MAXOF"

Now it is working fine.

Re: Sum rasters failing with "Unexpected error"

XanderBakker — Sat, 11 Dec 2021 23:12:17 GMT

I'm glad you resolved it by yourself,. Indeed using Cell statistics is the best way to sum multiple rasters.(since it can also handle NoData cells better).

To give you a reason why your first snippet failed, this is most likely since you are trying to sum a raster object and a string. Probably it would be fixed if you include "arcpy.Raster()" on line 9 as shown below:

rasters = arcpy.ListRasters('cf_*')

i = 0
for ras in rasters:
    if i == 0:
        sumras = arcpy.Raster(ras)
        i += 1
    else:
        sumras = sumras + arcpy.Raster(ras)
        i += 1
sumras.save(outRasterCFS)‍‍‍‍‍‍‍‍‍‍‍

I marked your answer as the correct one. It is better to not delete the question, since other users may find the answer you found yourself helpful to solve their problems.

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Sum rasters failing with "Unexpected error"

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