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

[Tony Lownds]

On Aug 10, 2007, at 11:23 AM, Guido van Rossum wrote:

> Python 3.0 currently has limited universal newlines support: by
> default, \r\n is translated into \n for text files, but this can be
> controlled by the newline= keyword parameter. For details on how, see
> PEP 3116. The PEP prescribes that a lone \r must also be translated,
> though this hasn't been implemented yet (any volunteers?).
>

I'm working on this, but now I'm not sure how the file is supposed to  
be read when
the newline parameter is \r or \r\n. Here's the PEP language:

   buffer is a reference to the BufferedIOBase object to be wrapped  
with the TextIOWrapper.
   encoding refers to an encoding to be used for translating between  
the byte-representation
   and character-representation. If it is None, then the system's  
locale setting will be used
   as the default. newline can be None, '\n', '\r', or '\r\n' (all  
other values are illegal);
   it indicates the translation for '\n' characters written. If None,  
a system-specific default
   is chosen, i.e., '\r\n' on Windows and '\n' on Unix/Linux. Setting  
newline='\n' on input
   means that no CRLF translation is done; lines ending in '\r\n'  
will be returned as '\r\n'.
   ('\r' support is still needed for some OSX applications that  
produce files using '\r' line
   endings; Excel (when exporting to text) and Adobe Illustrator EPS  
files are the most common examples.

Is this ok: when newline='\r\n' or newline='\r' is passed, only that  
string is used to determine
the end of lines. No translation to '\n' is done.

> However, the old universal newlines feature also set an attibute named
> 'newlines' on the file object to a tuple of up to three elements
> giving the actual line endings that were observed on the file so far
> (\r, \n, or \r\n). This feature is not in PEP 3116, and it is not
> implemented. I'm tempted to kill it. Does anyone have a use case for
> this? Has anyone even ever used this?
>

This strikes me as a pragmatic feature, making it easy to read a file
and write back the same line ending. I can include in patch.

http://www.google.com/codesearch?hl=en&q=+lang:python+%22.newlines%22 
+show:cz2Fhijwr3s:yutdXigOmYY:YDns9IyEkLQ&sa=N&cd=12&ct=rc&cs_p=http://f 
tp.gnome.org/pub/gnome/sources/meld/1.0/ 
meld-1.0.0.tar.bz2&cs_f=meld-1.0.0/filediff.py#a0

http://www.google.com/codesearch?hl=en&q=+lang:python+%22.newlines%22 
+show:SLyZnjuFadw:kOTmKU8aU2I:VX_dFr3mrWw&sa=N&cd=37&ct=rc&cs_p=http://s 
vn.python.org/projects/ctypes/trunk&cs_f=ctypeslib/ctypeslib/ 
dynamic_module.py#a0

Thanks
-Tony