arcpy.ListFeatureClasses doesn't work when using os.path.join

Question

Hi, I couldn't figure out why arcpy.ListFeatureClasses() doesn't work when I set env.workspace = os.path.join (path,gdb) and works when I set env.workspace = r"path to the gdb"! here is an example: The below script works in my IDE import arcpy #Solution 1 gdbANDpath=r"C:\ahmad data\data\MyProject5\f.gdb" arcpy.env.workspace=gdbANDpath fclist=arcpy.ListFeatureClasses() print len(fclist) ‍‍‍‍‍‍‍‍‍‍‍ prints >> 8 while the following script doesn't work and gives an error: import arcpy import os #Solution 2 gdb_name="f.gdb" gbd_path="C:\ahmad data\data\MyProject5" gdbANDpath=os.path.join(gdb_name,gbd_path) arcpy.env.workspace=gdbANDpath fclist=arcpy.ListFeatureClasses() print len(fclist)‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍ Traceback (most recent call last): File "", line 31, in TypeError: object of type 'NoneType' has no len() >>> fclist here returns none and fails to create a list of feature classes in the gdb! PS: Tested on ArcMap 10.7.1 and 10.6.1, on more than one gdb

AhmadSALEH1 · Answer

Thanks Joshua, this explains a lot.

bixb0012 · Answer

Regarding: I am under the assumption that os.path.join(gbd_path,gdb_name) does the same job as using the "r" before the path! You are incorrect. os.path.join won't convert or treat a regular string literal to a raw string literal. >>> import os >>> >>> path = "C:\ahmad data\data\MyProject5" >>> raw_path = r"C:\ahmad data\data\MyProject5" >>> name = "f.gdb" >>> >>> print(os.path.join(path, name)) C:hmad data\data\MyProject5\f.gdb >>> >>> print(os.path.join(raw_path,name)) C:\ahmad data\data\MyProject5\f.gdb >>> ‍‍‍‍‍‍‍‍‍‍‍‍ Your issue is that "\a" is a Python escape sequence for ASCII Bell (BEL) character. If you don't properly escape it, or use raw string notation, that character will make a little chime on your speakers and then be removed from the string. When you say "this used to work," I am guessing the path was different and didn't involve any Python escape sequences.

danretired · Answer

you provide this

n = "f.gdb"
g = "C:\ahmad data\data\MyProject5"

os.path.join(g, n)
'C:\x07hmad data\data\MyProject5\f.gdb'  # ---- fails

This works

n = "f.gdb"
g0 = r"C:\ahmad data\data\MyProject5"  # ---- raw format

os.path.join(g0, n)
 'C:\ahmad data\data\MyProject5\f.gdb'

Or check pathlib in 2.7

Python 2.7.18 documentation

if you must use arcmap

or

n = "f.gdb"
g ="C:/ahmad data/data/MyProject5"

p = "{}/{}".format(g, n)

p
'C:/ahmad data/data/MyProject5/f.gdb'

which will work fine