homepage

The output of "python3.5 --help" says:
 -u : unbuffered binary stdout and stderr, stdin always buffered;
 also PYTHONUNBUFFERED=x
 see man page for details on internal buffering relating to '-u'
If you look at the man page as instructed then you'll see a clearer
explanation:
 -u Force the binary I/O layers of stdout and stderr to be
 unbuffered. stdin is always buffered. The text I/O layer will
 still be line-buffered.
For example, if you try this:
 python3.5 -uc 'import sys,time;w=sys.stdout.buffer.write;w(b"a");time.sleep(1);w(b"b");'
then you'll see that the binary output is indeed unbuffered as
documented.
The output of --help is trying to abbreviate this explanation, but I
think it's abbreviated too much. The explanation from the man page
seems clear to me, and is only a little longer, so I suggest changing
the --help output to match the man page.