On Nov 7, 2007 6:10 AM, Daniel Stutzbach <[EMAIL PROTECTED]> wrote: > On Nov 7, 2007 6:59 AM, Wojciech Walczak > <[EMAIL PROTECTED]> wrote: > > py3k's print() is not flushing when end is set to '' and all it has to > > print is one-character-long string:
print() should never flush. The stream can be set to flush when a newline is seen (set buffer size to 1) though there may currently be some bugs in that code. Interactive mode should flush before printing the >>>prompt. > print() shouldn't flush if there isn't a newline, unless the buffer is > full or the user calls flush(). However, in an interactive > interpreter in pre-3.0, Python will automatically add a newline. Try > this in 2.5: > > --------------------------------------- > import time > print 'foo', > time.sleep(10) > print > --------------------------------------- > > You'll see that "foo" appears *after* 10 seconds, not before. > However, in an interactive interpreter, Python will add a newline > after 'foo' ever with the comma there, and the newline causes a flush. > Observe (2.5): > > >>> print 'foo', > foo > >>> print 'foo' > foo > >>> > > The same number of newlines are created with the comma and without, > which is different than the script behavior. Right. This is because 2.x doesn't only flush, it also adds a newline when the last character written wasn't a newline. > It sounds like P3K isn't doing this. That's because it doesn't have the 'softspace' feature used by 2.x to implement the automatic appending of a newline as needed. The softspace feature was intentionally removed because it is a royal pain to deal with. Adding the flush back to interactive mode should be easy (flush both stdout and stderr). Adding the auto-newline back is not; I'm not convinced that it is necessary to do so since it'll be pretty rare and usually the user is asking for trouble. > The patch you suggest would cause a flush after *every* write with > print, which would cause a very significant performance hit on > programs that do a lot of writing to standard output (especially if > standard output is a pipe). Right, don't do that! > Tangent: If standard output is a pipe and not a tty, is P3K smart > enough to switch to fully-buffered mode instead of line-buffered mode? It checks isatty() when the buffer size is not given explicitly, so it should be. Worth testing though. -- --Guido van Rossum (home page: http://www.python.org/~guido/) _______________________________________________ Python-3000 mailing list Python-3000@python.org http://mail.python.org/mailman/listinfo/python-3000 Unsubscribe: http://mail.python.org/mailman/options/python-3000/archive%40mail-archive.com
