os.path.isfile() error

[7stud]

Here's the code:
------------
import os, os.path, pprint

mydir = "/Users/me/2testing"

files = [file for file in os.listdir(mydir)]
pprint.pprint(files)

print os.path.join(mydir, "helloWorld.py")

files = [file
for file in os.listdir(mydir)
if os.path.isfile(os.path.join(dir, file) )
]

pprint.pprint(files)
----output:----------------

['.DS_Store', 'cpTest', 'dir1', 'testfile1', 'xmlFile.xml']
/Users/me/2testing/helloWorld.py
Traceback (most recent call last):
  File "test1.py", line 16, in ?
    files = [file
  File "/System/Library/Frameworks/Python.framework/Versions/2.3/lib/
python2.3/posixpath.py", line 62, in join
    elif path == '' or path.endswith('/'):
AttributeError: 'builtin_function_or_method' object has no attribute
'endswith'