portable way to tell what Popen will call

[Brendan Miller]

I need a portable way to tell what subprocess.Popen will call.

For instance on unix systems, Popen will work for files flagged with the
executable bit, whereas on windows Popen will work on files ending the in
.exe extension (and I don't think anything else). Is there a portable way
to check what Popen will work on without actually execute it? Do I have to
write a bunch of platform specific code here?

Thanks,
Brendan