# Problem in Calculate percent difference between two rasters

Question asked by dljayasekera on Sep 8, 2017
Latest reply on Sep 11, 2017 by dkwiens

Hi,

I need to calculate the percent difference between two rasters. Below is my code and I am getting the following error. Can somebody help me to correct my code?

``Traceback (most recent call last):  File "C:\Users\jayaskeradl\Desktop\Arkansas Flood\My_Phyton_Scripts\Normal_Difference.py", line 73, in <module>    outcalc2 = Minus(normal, fmaskrasters)  File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py", line 4247, in Minus    in_raster_or_constant2)  File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Utils.py", line 53, in swapper    result = wrapper(*args, **kwargs)  File "c:\program files (x86)\arcgis\desktop10.4\arcpy\arcpy\sa\Functions.py", line 4244, in Wrapper    ["Minus", in_raster_or_constant1, in_raster_or_constant2])TypeError: expected a raster or layer name``
``months = [10]weeks = [1]year = [2010]arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All' out = r'H:\PRISM_800m_weekly_sum\Crawford\All\output'for month in months:     for week in weeks:     arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All'     fmaskrasters = arcpy.ListRasters("Week_" + str(week) + "_Sum" + str(year) + "_" + str(month) + "*","*")    arcpy.env.workspace = r'H:\PRISM_800m_weekly_sum\Crawford\All\output'     normal = arcpy.ListRasters("Crawford_Normal_Week_" + str(week) + "_*_" + str(month) + "*")    outcalc2 = Minus(normal, fmaskrasters)    Final = (outcalc2/normal)*100    finras1 = out + "\\" + "Crawford_Normal_Week_" + str(week) + "_Difference" + "_" + str(month) + ".tif"    arcpy.CopyRaster_management(Final,finras1 + "_Normal_Difference_Crawford.tif","","","","","")``