# Accessing individual raster bands using arcpy Raster class?

I am working with rasters in arcpy and I am not able to access individual bands using the Raster class. The same code that worked about a year ago no longer works.

I should be able to access a single band of a raster like so:

Band3 = Raster(raster_filename + "/Band_3")

But the resulting Band3 variable has all 6 bands in the raster, not just band 3.

The "/Band_3" syntax appears to work fine in the Describe method in the first half of the following code but doesn't work in the Raster class later on:

    folder = r"C:\Users\elyons\Desktop\Spring_2018\Labs\New_LabData"

import arcpy
from arcpy.sa import *
arcpy.CheckOutExtension("Spatial")

arcpy.env.workspace = folder
arcpy.env.overwriteOutput = True

raster_filename = "Landsat.tif"

#Create describe objects
desc = arcpy.Describe(raster_filename)
desc_band = arcpy.Describe(raster_filename + "/Band_3")

#These are properties of the describe raster BAND object
print "Height = " + str(desc_band.height)
print "Width = " + str(desc_band.width)
print "Resolution = " + str(desc_band.meanCellWidth)

#This one is a property of the describe raster dataset object
print "Number of Bands is = " + str(desc.bandCount)

#Open bands as raster band objects
Band3 = Raster(raster_filename + "/Band_3")

#print number of bands
print Band3.bandCount

#Save the raster
print "saving"
Band3.save("savebandtest.tif")
print "saved"

arcpy.CheckOutExtension("Spatial")


The above code prints out the correct information for the describe objects and then prints 6 for Band3.bandCount, which is not right. It then saves a six band raster to the filename savebandtest.tif that is identical to Landsat.tif. I have tried different multiband rasters, different computers, getting the band name programatically, setting the working directory to the raster, forward slashes, backward slashes, everything I can think of.

Has the syntax changed for accessing single bands from multiband raster files? I can't find any mention of a change in the help.