[Python-3000] [Python-Dev] Universal newlines support in Python 3.0

[Guido van Rossum]

On 8/14/07, Barry Warsaw <barry at python.org> wrote:
> On Aug 14, 2007, at 12:52 PM, Guido van Rossum wrote:
> > On 8/14/07, Barry Warsaw <barry at python.org> wrote:
> >> It would have been perfect, I think, if I could have opened the file
> >> in text mode so that read() gave me strings, with universal newlines
> >> and preservation of line endings (i.e. no translation to \n).
> >
> > You can do that already, by passing newline="\n" to the open()
> > function when using text mode.
>
> Cute, but obscure.  I'm not sure I like it as the ultimate way of
> spelling these semantics.

It was the best we could come up with in the 3 minutes we devoted to
this at PyCon when drafting PEP 3116. If you have a better idea,
please don't hide it!

> > Try this script for a demo:
> >
> > f = open("@", "wb")
> > f.write("bare nl\n"
> >         "crlf\r\n"
> >         "bare nl\n"
> >         "crlf\r\n")
> > f.close()
> >
> > f = open("@", "r")  # default, universal newlines mode
> > print(f.readlines())
> > f.close()
> >
> > f = open("@", "r", newline="\n")  # recognize only \n as newline
> > print(f.readlines())
> > f.close()
> >
> > This outputs:
> >
> > ['bare nl\n', 'crlf\n', 'bare nl\n', 'crlf\n']
> > ['bare nl\n', 'crlf\r\n', 'bare nl\n', 'crlf\r\n']
> >
> > Now, this doesn't support bare \r as line terminator, but I doubt you
> > care much about that (unless you want to port the email package to Mac
> > OS 9 :-).
>
> Naw, I don't, though someday we'll get just such a file and a bug
> report about busted line endings ;).
>
> There's still a problem though: this works for .readlines() but not
> for .read() which unconditionally converts \r\n to \n.  The
> FeedParser uses .read() and I think the behavior should be the same
> for both methods.

Ow, that's a bug! I'll look into fixing it; this was unintentional!

-- 
--Guido van Rossum (home page: http://www.python.org/~guido/)