How to tell when a file is closed

[Peter Curran]

Simple problem:  I have an exe that creates a new file.  I call this exe
from python with execfile, but I don't know how to tell when the exe I
called is finished writing its file.  Without using any of the extra Win32
modules, how can I tell when the exe is finished?  Would os.path.isfile
work?  Are there other utilities?  If it helps, I'm actually doing this from
jpython -- maybe there's a java class that does this nicely?  Any ideas out
there?

Thank You!

-Peter