Does fileinput.input() read STDIN all at once?

[Adam Funk]

I'm using this sort of standard thing:

   for line in fileinput.input():
      do_stuff(line)

and wondering whether it reads until it hits an EOF and then passes
lines (one at a time) into the variable line.  This appears to be the
behaviour when it's reading STDIN interactively (i.e. from the
keyboard).

As a test, I tried this:

   for line in fileinput.input():
      print '**', line

and found that it would print nothing until I hit Ctl-D, then print
all the lines, then wait for another Ctl-D, and so on (until I pressed
Ctl-D twice in succession to end the loop).

Is it possible to configure this to pass each line of input into line
as it comes?

Thanks,
Adam