How to do a raster layer summation by loop?

RebeccaRicker — Sun, 12 Nov 2017 04:41:09 GMT

Hey folks,

I work with ArcGIS Pro and Python and I need to do a Summation over 31 raster layers. I want to do it by a loop, because I need it more often.

This is what I want to loop:

arcpy.env.workspace = Folder_Single_Layer_ND_as_0

Sum_Layer_ND_as_0 = \

Raster("/offset_0_1.tif") \

+ Raster("/offset_0_2.tif") \

+ Raster("/offset_0_3.tif") \

+ Raster("/offset_0_4.tif") \

+ Raster("/offset_0_5.tif") \

+ Raster("/offset_0_6.tif") \

+ Raster("/offset_0_7.tif") \

+ Raster("/offset_0_8.tif") \

+ Raster("/offset_0_9.tif") \

+ Raster("/offset_0_10.tif") \

+ Raster("/offset_0_11.tif") \

+ Raster("/offset_0_12.tif") \

+ Raster("/offset_0_13.tif") \

+ Raster("/offset_0_14.tif") \

+ Raster("/offset_0_15.tif") \

+ Raster("/offset_0_16.tif") \

+ Raster("/offset_0_17.tif") \

+ Raster("/offset_0_18.tif") \

+ Raster("/offset_0_19.tif") \

+ Raster("/offset_0_20.tif") \

+ Raster("/offset_0_21.tif") \

+ Raster("/offset_0_22.tif") \

+ Raster("/offset_0_23.tif") \

+ Raster("/offset_0_24.tif") \

+ Raster("/offset_0_25.tif") \

+ Raster("/offset_0_26.tif") \

+ Raster("/offset_0_27.tif") \

+ Raster("/offset_0_28.tif") \

+ Raster("/offset_0_29.tif") \

+ Raster("/offset_0_30.tif") \

+ Raster("/offset_0_31.tif") \

Sum_Layer_ND_as_0.save()

I tried so far...

# Those are already definite

# TxWx = "/offset" # I need this as a Variable.

# Number_of_Years = 31 # I calculated this from a NetCDF

...this:

arcpy.env.workspace = Folder_Single_Layer_ND_as_0

for Number in range(1, int(Number_of_Years))

Sum_Layer_ND_as_0 += Raster(TxWx + "_0_" + Number + ".tif")

...and this:

arcpy.env.workspace = Folder_Single_Layer_ND_as_0

x = 1

while True:

Sum_Layer_ND_as_0 += Raster(TxWx + "_0_" + str(x) + ".tif")

x += int(Number_of_Years)

... and this:

arcpy.env.workspace = Folder_Single_Layer_ND_as_0

count = 1

while count <= int(Number_of_Years):

Sum_Layer_ND_as_0 += Raster(TXWX + "_0_" + str(count) + ".tif")

count +=1

Nothing works. I am a very beginner in Python. I would be very grateful if anyone could help me!!!

PS.: If my question is on the wrong position or I am not supposed to ask it here, please tell me.

Re: How to do a raster layer summation by loop?

DanPatterson_Retired — Sat, 11 Dec 2021 08:19:39 GMT

https://community.esri.com/blogs/dan_patterson/2016/08/14/script-formatting to format your code so it is easier to read.

You need to use list rasters and sum the raster datasets using a Local sum

import arcpy
from arcpy import env
env.workspace = "C:/some_folder/a_folder_or_gdb"
arcpy.CheckOutExtension("Spatial")
in_rasters = arcpy.ListRasters("*", "TIF")  # change to suit the raster types
sum_cellstats = CellStatistics_sa(in_rasters, "SUM", "DATA")  # read the help!!
sum_cellstats.save("C:/test/output/sum_o_rama")‍‍‍‍‍‍‍

which has obviously not been tried but you can examine the various help topics to get the idea of how to work through through the process

Re: How to do a raster layer summation by loop?

RebeccaRicker — Sun, 12 Nov 2017 14:46:55 GMT

Thank you soooooo much again

It worked!

Re: How to do a raster layer summation by loop?

DanPatterson_Retired — Sun, 12 Nov 2017 15:14:11 GMT

no problem

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How to do a raster layer summation by loop?

Re: How to do a raster layer summation by loop?

Re: How to do a raster layer summation by loop?

Re: How to do a raster layer summation by loop?