Help with Python Script Syntax / Clean up ( ESRI ArcMap - Raster Calculator)

Hello,
I am trying to create a python script to automate some functions in ESRI ArcMap. (I previously recieved assistance with a more complicated, but similar script https://www.experts-exchange.com/questions/23068228/Modify-Python-Script-for-more-automation.html).

I am trying to use a module in ArcGis Called "Int_sa". A sample scripting command from ESRI:
____________________
# Import system modules
import arcgisscripting

# Create the Geoprocessor object
gp = arcgisscripting.create()

try:
    # Set the input raster dataset
    inRaster = "C:/data/ras_1"

    # Set the output raster name
    outRaster = "C:/data/final_1"

    # Check out ArcGIS Spatial Analyst extension license
    gp.CheckOutExtension("Spatial")

    # Process: Int
    gp.Int_sa(inRaster, outRaster)

except:
    # If an error occurred while running a tool, then print the messages.
    print gp.GetMessages()
___________________

The script I created (by hacking up another working script), below, tries to make this to run for more than one iteration. For clarification, 'f' is a text file with the locations of 'dem.'

I ran it from the command line as such:
C:\Python24\python "C:\dem.py" "C:\dem.txt"

I get the following error message:
Traceback (most recent call last):
  File "C\dem.py", line 38, in ?
    gp.Int_sa(inRaster, outRaster)
RuntimeError: error in executing tool

My log went to 'legit/n'
If I uncomment try and except, I get not errors and no output.
What does try and except do? And am I using the log feature correctly?

Please advise & I appreciate annotated code,
Thank you kindly,
MJ

P.S.
Someone who got the same error as me for a different process was told on an ESRI forum to:

put the processes within a try/except block with appropriate
gp.addmessage("error here at step .... " + gp.getmessages())
lines throughout to see further details of errors

But I don't really know what this is telling me to do and there was no follow up on the post.

# Multi_Output_Map_Algebra_sample.py
# Description: 
#   Runs an expression built with the Map Algebra language.
# Requirements: None
# Author: ESRI
# Date: Sept 6, 2005
# Import system modules
import sys, arcgisscripting, os
#import sys
 
def log(s):
      f = open("C:/DEM_ERROR.txt","w")
      f.write(s)
      f.close()
 
# Create the Geoprocessor object
gp = arcgisscripting.create()
inRaster = open(sys.argv[1],'r')
log("1/n")
count = 1
tmpdir = 'c:\\temp\\'
 
##try:
for dem in inRaster:
			
	# Set local variables
	outRaster = os.path.join(tmpdir, 'dem', str(count))
	log("outRaster")
	inExpression = "Int_sa(" + dem.strip() + "+ 0.5), outRaster"
	log("inExpression")
	print inExpression
	log("4/n")
	# Check out Spatial Analyst extension license
	gp.CheckOutExtension("Spatial")
	log("legit/n")
 
	# Process: MapAlgebra
	gp.Int_sa(inRaster, outRaster)
	log("5/n")
	count = count + 1
	log("6/n")
	f.close
		
##except:
    # If an error occurred while running a tool, then print the messages.
	print gp.GetMessages()

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