On 8/14/07, Guido van Rossum <[EMAIL PROTECTED]> wrote: > I thought some more about the universal newlines situation, and I > think I can handle all the use cases with a single 'newline' > parameter. The use cases are: > > (A) input use cases: > > (1) newline=None: input with default universal newlines mode; lines > may end in \r, \n, or \r\n, and these are translated to \n. > > (2) newline='': input with untranslated universal newlines mode; lines > may end in \r, \n, or \r\n, and these are returned untranslated.
Caveat: this mode cannot be supported by sockets. When reading a lone \r you need to peek ahead to ensure the next character is not a \n, but for sockets that may block indefinitely. I don't expect sockets to use the file API by default, but there's enough overlap (named pipes?) that limitations like this should be well documented (and if possible, produce an explicit error!) > (3) newline='\r', newline='\n', newline='\r\n': input lines must end > with the given character(s), and these are translated to \n. > > (B) output use cases: > > (1) newline=None: every \n written is translated to os.linesep. > > (2) newline='': no translation takes place. > > (3) newline='\r', newline='\n', newline='\r\n': every \n written is > translated to the value of newline. > > Note that cases (2) are new, and case (3) changes from the current PEP > and/or from the current implementation (which seems to deviate from > the PEP). [snip] > > * If universal newlines without translation are requested on > input (i.e. ``newline=''``), if a system read operation > returns a buffer ending in ``'\r'``, another system read > operation is done to determine whether it is followed by > ``'\n'`` or not. In universal newlines mode with > translation, the second system read operation may be > postponed until the next read request, and if the following > system read operation returns a buffer starting with > ``'\n'``, that character is simply discarded. -- Adam Olsen, aka Rhamphoryncus _______________________________________________ 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
