Getting band names using ArcPy in ArcGIS Desktop 10.x

If you want the band names you can set arcpy.env.workspace to the raster, then use arcpy.ListRasters() to list the bands, here's an example wrapped up into a function:

import arcpy

def get_bands(path_to_raster):
    """ Get a list of band names from a multiband raster """

    # Save previous workspace
    oldws = arcpy.env.workspace 

    #Get raster objects from band names
    arcpy.env.workspace = path_to_raster
    bands = arcpy.ListRasters()

    #Restore previous workspace
    arcpy.env.workspace = oldws

    return bands

Or if you want the full path:

import os
import arcpy

def get_bands(path_to_raster):
    """ Get a list of band names from a multiband raster """

    # Save previous workspace
    oldws = arcpy.env.workspace 

    #Get raster objects from band names
    arcpy.env.workspace = path_to_raster
    bands = [os.path.join(path_to_raster, b) for b in arcpy.ListRasters()]

    #Restore previous workspace
    arcpy.env.workspace = oldws

    return bands

If you don't actually care what the band names are and want to access a raster band by index (band number), use arcpy.MakeRasterLayer_management

arcpy.MakeRasterLayer_management(input_raster, "lyr_band3", band_index="3")