Hi, I am doing something similar, but I have a directory with 11 folders each containing 7 .tif layers to be combined. I tried using os.walk to go through all the folders in the directory and was able to append each folder's content into a rasterList (I emptied the list between each folder). I'm having trouble getting the tool to run on all 7 .tif files in the list. I am posting what I started with before I found this post, and then the after what I tried. In the first code I was trying to get the rasterList into the in_rasters format ex.("band1.tif; band2.tif; band3.tif") in case that was causing the tool not to run. Any help would be awesome!import arcpy, os
#arcpy.env.workspace = "C:/Test"
arcpy.env.overwriteOutput = True
myDir = arcpy.GetParameterAsText(0)
bands = []
#?myDownloads = os.listdir(myDir) 
try:
    
    #Walk through directories
    for root, dirs, files in os.walk(myDir):
        arcpy.env.workspace = root
        for f in files:
            if f.endswith(".TIF"):
                bands.append(f)
                            #print bands
            a = ','.join(bands)
            b = a.replace(",",";")
                #[f.replace(",", ";") for f in bands]
            arcpy.CompositeBands_management(b, f[:-7] + ".img")
        print bands
        bands=[]
        print b   
   
except:
    print "Tool did not run"
    print arcpy.GetMessages() and after:import arcpy, sys, os
from arcpy import env
from arcpy.sa import *
arcpy.env.overwriteOutput = True 
path_images = "C:/test" #arcpy.GetParameterAsText(0) 
rasterList = []
for root, dirs, files in os.walk(path_images):
    for name in files:
        bands = os.path.join(root,name)
        #print bands
        if bands.endswith(".TIF"):
            rasterList.append(bands)
            tilename = name[0:-7]
            #print tilename + " is being processed."
        print rasterList    
        out_raster = path_images + "\\" + tilename + ".img"
        print out_raster
    #arcpy.CompositeBands_management(rasterList, out_raster)
    rasterList = []
print rasterList