detecting newline character

Daniel Geržo danger at
Sat Apr 23 16:25:20 EDT 2011

On 23.4.2011 21:33, Thomas 'PointedEars' Lahn wrote:
> Chris Rebert wrote:
>> On Sat, Apr 23, 2011 at 11:09 AM, Daniel Geržo<danger at>  wrote:
>>> I need to detect the newline characters used in the file I am reading.
>>> For this purpose I am using the following code:
>>> def _read_lines(self):
>>>      with contextlib.closing(, "rU")) as fobj:
>>>      fobj.readlines()
>>>      if isinstance(fobj.newlines, tuple):
>>>          self.newline = fobj.newlines[0]
>>>      else:
>>>          self.newline = fobj.newlines
>>> This works fine, if I call without encoding argument; I am
>>> testing with an ASCII enghlish text file, and in such case the
>>> fobj.newlines is correctly detected being as '\r\n'. However, when I call
>>> with encoding='ascii' argument, the fobj.newlines is None
>>> and I can't figure out why that is the case. Reading the PEP at
>>> I don't see any reason why would
>>> I end up with newlines being None after I call readlines().
>>> Anyone has an idea?
>> I would hypothesize that it's an interaction bug between universal
>> newlines and
>> […]
>> I would speculate that the upshot of this is that ends
>> up calling built-in open() with a nonsense `mode` of "rUb" or similar,
>> resulting in strange behavior.
>> If this explanation is correct, then there are 2 bugs:
>> 1. Built-in open() should treat "b" and "U" as mutually exclusive and
>> reject mode strings which involve both.
>> 2. should either reject modes involving "U", or be fixed
>> so that they work as expected.
> You might be correct that it is a bug (already fixed in versions newer than
> 2.5), since from my Python 2.6 reads as follows:

Well I am doing this on:
Python 2.7.1 (r271:86832, Mar  7 2011, 14:28:09)
[GCC 4.2.1 (Apple Inc. build 5664)] on darwin

So what do you guys advise me to do?

S pozdravom / Best regards
   Daniel Gerzo

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