Error: 'NoneType' object is not iterable (arcpy.ListRasters)

Question

I am trying to extract a raster through a particular shapefile.

   import arcpy
   from arcpy import env
   from arcpy.sa import *
   arcpy.CheckOutExtension("Spatial")
   env.overwriteOutput = True

   #Set the current workspace
   env.workspace = ("C:\thesis\Forests Only Percent Treecover\2003 BSWM Forest")
   env.nodata = "MINIMUM"
   env.compression = "LZ77"

   #This is for extracting the forest areas of hansen percent treecover
   for raster in arcpy.ListRasters("*0E.tif", "TIFF"):
       print raster #checking the presence of raster
       outputRasterExtractbyMask = ExtractByMask(raster, "NAMRIA.shp")
       outputRasterExtractbyMask_Name = "forests_only"+raster
       outputRasterExtractbyMask.save(outputRasterExtractbyMask_Name)

   print "Finish"

As I print the raster in arcpy.ListRasters to check the presence of raster, this error shows up:

 Traceback (most recent call last):
 File "C:\Users\brentiebark\Dropbox\Python Scripts and mxds\extractbymask.py", line 14, in <module>
 for raster in arcpy.ListRasters("*0E.tif", "TIFF"):
 TypeError: 'NoneType' object is not iterable

I double checked the directory, and my files are really there. Is there something wrong with my code?

Answer 1

Try replacing:

env.workspace = ("C:\thesis\Forests Only Percent Treecover\2003 BSWM Forest")

with:

env.workspace = (r"C:\thesis\Forests Only Percent Treecover\2003 BSWM Forest")

The backslash is Python's escape character so when it appears in a DOS path you need to replace it with either a forward slash or double back slashes or just put an r for raw in front of the whole string.

There is also an error where:

for raster in arcpy.ListRasters("*0E.tif", "TIFF"):

should be:

for raster in arcpy.ListRasters("*0E.tif", "TIF"):