Python- Updating alpha from a group

I've tied the alpha updating to an action inside photoshop, and the results are pretty pleasing. Within the script there is a bit of juggling between active layers and active channels in order to get the action working properly.

I also like to leave the user off in a place that makes sense- in this case, the alpha group, since its the one being updated.  

The basics of this script:
Checks for an 'alpha' group in the active PSD file. If present, copies it's merged contents to the alpha channel.

##############################################################################
#
# Photoshop alpha updater
# (C) Pete Hanshaw, 2012
# http://peterhanshawart.blogspot.com.au/
#
##############################################################################
#
# Checks for an 'alpha' group in the active PSD file. If present, copies it's 
# contents to the alpha channel. 
#
# Requires the Win32 Extensions:
# http://python.net/crew/mhammond/win32/
#
##############################################################################
 
#Import required modules
from win32com.client.dynamic import Dispatch
from stat import *
import os
from sys import exit
import pythoncom

#Define the name of the Alpha group here
alpha_group = 'alpha'

#Begin the script
if (__name__ == '__main__'):

    #COM dispatch for Photoshop
    try:
        psApp = Dispatch('Photoshop.Application')
 
    except:
        os.system("color 0c")
        print "Photoshop dispatch failed"
        os.system("PAUSE")
        exit(0)

    #Get the currently active document
    try:
        doc = psApp.activeDocument
 
    #Gracefully end if a document is not open
    except:
        os.system("color 0c")
        print "You need to have an active Photoshop Doc to use this script."
        os.system("PAUSE")
        exit(0)

    #Get information about our current doc
    activeChannels = doc.ActiveChannels
    layerSets = doc.LayerSets
    channelRef = doc.Channels
    
    #Check if there are any layerSets in the current doc
    if (len(layerSets) > 0):

        #Assume there is no alpha
        alphaExists = False

        #Check for an alpha channel
        for channel in channelRef:
            if channel.name == "Alpha 1":
                alphaExists = True
                break

        if alphaExists == False:
            #add a blank alpha channel
            doc.Channels.Add()

        #save the current setup
        saved_state = doc.activeHistoryState

        #Prepare the alpha group for duplication
        doc.activeChannels = activeChannels
        doc.activeLayer = (doc.layerSets[alpha_group])
        doc.activeLayer.Visible = True
        doc.activeLayer.Merge()
        doc.activeLayer.Copy()

        #Now that we have a merged copy, revert the merging
        doc.activeHistoryState = saved_state

        #Now paste the merged alpha source into the alpha channel
        doc.activeLayer = (doc.artLayers['Background'])
        doc.activeChannels = [doc.Channels[5]]
        doc.Paste()

        #Restore control to the user
        doc.selection.deselect
        doc.activeChannels = activeChannels
        doc.activeLayer = (doc.layerSets[alpha_group])

        print "All done!"
        
    else:
        os.system("color 0c")
        print "Doc has no groups."
        os.system("PAUSE")
        exit(0)