Reopening, since sys.stdin is actually broken in unbuffered mode:

$ ./python -u
Python 3.1a0 (py3k:68756, Jan 19 2009, 01:17:26) 
[GCC 4.3.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import sys
>>> sys.stdin.read(1)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/antoine/py3k/__svn__/Lib/io.py", line 1739, in read
    eof = not self._read_chunk()
  File "/home/antoine/py3k/__svn__/Lib/io.py", line 1565, in _read_chunk
    input_chunk = self.buffer.read1(self._CHUNK_SIZE)
AttributeError: 'FileIO' object has no attribute 'read1'
>>> 

What I propose is that stdin be always opened in buffered mode (even
with -u), since I don't see how the behaviour can differ for a read-only
non-seekable stream.