In search of idiom in py2exe

[David]

In many of my scripts I've used the following idiom for accessing data
files placed nearby:

BASEDIR = os.path.dirname(__file__)
.
.
.
fp = file(os.path.join(BASEDIR,"somefile.txt"))
.
.
.
img = image.open(os.path.join(BASEDIR,"images","someimage.jpg"))


This works well with my cohorts who place their work on different
drives, in different directories, etc. 

However, when I use py2exe to make an executable, the name '__file__'
is not defined.

Can anyone recommend an idiom that will work with py2exe?

Thanks in advance,
Dave M.

P.S. -- We've also tried the idiom

BASEDIR = os.path.dirname(sys.argv[0])

but the result can be misleading, for example, if the script is
launched from a desktop shortcut.