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Re: when does newlines get set in universal newlines mode?

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On Tue, May 5, 2015 at 1:17 AM, Peter Otten <__peter__@web.de> wrote:
> OK, you convinced me. Then I tried:
>
>>>> with open("tmp.txt", "wb") as f: f.write("0\r\n3\r5\n7")
> ...
>>>> assert len(open("tmp.txt", "rb").read()) == 8
>>>> f = open("tmp.txt", "rU")
>>>> f.readline()
> '0\n'
>>>> f.newlines
>>>> f.tell()
> 3
>>>> f.newlines
> '\r\n'
>
> Hm, so tell() moves the file pointer? Is that sane?

... wow. Okay! That's a bit weird.

It's possible that something's being done with internal buffering
(after all, it's horribly inefficient to *actually* read text one byte
at a time, even if that's what's happening conceptually), and that
tell() causes some checks to be done. But that really is rather
strange. I'd be interested to know what happens if another process
writes to a pipe "0\r", then sleeps while the readline() and tell()
happen, and then writes a "\n" - what will that do to newlines?

By the way, it's as well to clarify, with all these examples, what
Python version you're using. There may be significant differences.

ChrisA

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Thread

when does newlines get set in universal newlines mode? arekfu@gmail.com - 2015-05-04 02:50 -0700
  Re: when does newlines get set in universal newlines mode? Peter Otten <__peter__@web.de> - 2015-05-04 14:01 +0200
  Re: when does newlines get set in universal newlines mode? Chris Angelico <rosuav@gmail.com> - 2015-05-04 22:13 +1000
    Re: when does newlines get set in universal newlines mode? Davide Mancusi <arekfu@gmail.com> - 2015-05-04 06:35 -0700
      Re: when does newlines get set in universal newlines mode? Terry Reedy <tjreedy@udel.edu> - 2015-05-04 13:38 -0400
    Re: when does newlines get set in universal newlines mode? Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2015-05-05 18:31 +1000
      Re: when does newlines get set in universal newlines mode? Chris Angelico <rosuav@gmail.com> - 2015-05-05 18:41 +1000
        Re: when does newlines get set in universal newlines mode? Davide Mancusi <arekfu@gmail.com> - 2015-05-05 02:23 -0700
          Re: when does newlines get set in universal newlines mode? Chris Angelico <rosuav@gmail.com> - 2015-05-05 19:28 +1000
            Re: when does newlines get set in universal newlines mode? Davide Mancusi <arekfu@gmail.com> - 2015-05-05 03:58 -0700
  Re: when does newlines get set in universal newlines mode? Peter Otten <__peter__@web.de> - 2015-05-04 17:17 +0200
  Re: when does newlines get set in universal newlines mode? Chris Angelico <rosuav@gmail.com> - 2015-05-05 01:26 +1000
  Re: when does newlines get set in universal newlines mode? Ian Kelly <ian.g.kelly@gmail.com> - 2015-05-04 09:33 -0600

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