Loop through 2 folders and perform raster calculation

Question

I am currently learning arcgis and python.

The problem includes looping through 2 folders (with rasters of same filename) and performing raster calculation on each raster pair. Below is my code:

import arcpy, os, glob  
from arcpy.sa import *  
arcpy.CheckOutExtension("Spatial")  

ws1 = "E:\clip_qx"  
ws2 = "E:\clip_qy"  

outws = "E:\result"

rasterlist = arcpy.ListRasters()  
for r in ws1:  
    r1 = arcpy.sa.Raster(r)  
    r2 = arcpy.sa.Raster(os.path.join(ws2, basename))  
    result = sqrt ( r1^2 + r2^2 )  
    outname = basename    
    result.save(os.path.join(outws, outname))  

However, I am getting an error. It seems that the rasters were not read.

RuntimeError: ERROR 000732: Input Raster: Dataset E does not exist or is not supported.

Answer 1

You're iterating through the string ws1, instead of your list of rasters. Hence 'E' as not a supported input (the first character in string ws1). You need to create a list of rasters by setting the workspace and then using arcpy.ListRasters (). Try:

import arcpy, os, math
arcpy.CheckOutExtension("Spatial")  

ws1 = r"E:\clip_qx"  
ws2 = r"E:\clip_qy"  

outws = r"E:\result"

#set workspace
arcpy.env.workspace = ws1

rasterlist = arcpy.ListRasters()

for r in rasterlist:  
    r1 = arcpy.sa.Raster (r)  
    r2 = arcpy.sa.Raster(os.path.join(ws2, r))  
    result = math.sqrt ( r1^2 + r2^2 )      
    result.save(os.path.join(outws, r))  

However, this line will fail because you're trying to use python math operations on raster data:

result = math.sqrt ( r1^2 + r2^2 )

Look into raster math to learn how to execute this.

Answer 2

are you doing some kind of ocean or wind modeling? i was lucky to find your question because i am dealing with the same issue.

i got the math function to work by:

import arcpy, os, math
from arcpy import env
from arcpy.sa import *
arcpy.CheckOutExtension("Spatial")

and

result =  SquareRoot(r1 * r1 + r2 * r2)