import arcpy
from arcpy import env
from arcpy import sa
from arcpy.sa import *
arcpy.CheckOutExtension("Spatial")
env.workspace = r"C:\DATA\DEM"
lstRasters = arcpy.ListRasters("*")
for raster in lstRasters:
outSlope = Slope(raster, "DEGREE", .3048)
outSlope.save(r"C:\DATA\DEM" + "\\" + str(raster) + "_slope.tif")