Related issues are:

http://bugs.python.org/issue13824 - argparse.FileType opens a file and never closes it
http://bugs.python.org/issue14156 - argparse.FileType for '-' doesn't work for a mode of 'rb'

As discussed earlier FileType was meant as a convenience for small scripting applications, ones that don't try to close the file before exiting.

But now we are encouraged to open files in a context that guarantees closure.  In 13824 I proposed a 'FileContext', and included a dummy context like this handle stdin/out.

But I think the closefd=False approach raised in 14156 and David is probably the better way to go.

I think the main thing that is lacking is a testing mechanism.