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Re: python 3.3 repr

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On Friday, November 15, 2013 6:28:15 AM UTC-5, Robin Becker wrote:
> I'm trying to understand what's going on with this simple program
> 
> if __name__=='__main__':
> 	print("repr=%s" % repr(u'\xc1'))
> 	print("%%r=%r" % u'\xc1')
> 
> On my windows XP box this fails miserably if run directly at a terminal
> 
> C:\tmp> \Python33\python.exe bang.py
> Traceback (most recent call last):
>    File "bang.py", line 2, in <module>
>      print("repr=%s" % repr(u'\xc1'))
>    File "C:\Python33\lib\encodings\cp437.py", line 19, in encode
>      return codecs.charmap_encode(input,self.errors,encoding_map)[0]
> UnicodeEncodeError: 'charmap' codec can't encode character '\xc1' in position 6: 
> character maps to <undefined>
> 
> If I run the program redirected into a file then no error occurs and the the 
> result looks like this
> 
> C:\tmp>cat fff
> repr='┴'
> %r='┴'
> 
> and if I run it into a pipe it works as though into a file.
> 
> It seems that repr thinks it can render u'\xc1' directly which is a problem 
> since print then seems to want to convert that to cp437 if directed into a terminal.
> 
> I find the idea that print knows what it's printing to a bit dangerous, but it's 
> the repr behaviour that strikes me as bad.
> 
> What is responsible for defining the repr function's 'printable' so that repr 
> would give me say an Ascii rendering?
> -confused-ly yrs-
> Robin Becker

In Python3, repr() will return a Unicode string, and will preserve existing Unicode characters in its arguments.  This has been controversial.  To get the Python 2 behavior of a pure-ascii representation, there is the new builtin ascii(), and a corresponding %a format string.

--Ned.

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python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 11:28 +0000
  Re: python 3.3 repr Ned Batchelder <ned@nedbatchelder.com> - 2013-11-15 03:38 -0800
    Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 12:16 +0000
      Re: python 3.3 repr Ned Batchelder <ned@nedbatchelder.com> - 2013-11-15 05:54 -0800
        Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 14:29 +0000
        Re: python 3.3 repr Serhiy Storchaka <storchaka@gmail.com> - 2013-11-15 16:40 +0200
        Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 14:52 +0000
    Re: python 3.3 repr Roy Smith <roy@panix.com> - 2013-11-15 09:25 -0500
    Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 14:43 +0000
      Re: python 3.3 repr Ned Batchelder <ned@nedbatchelder.com> - 2013-11-15 07:08 -0800
        Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 15:39 +0000
        Re: python 3.3 repr Antoon Pardon <antoon.pardon@rece.vub.ac.be> - 2013-11-15 16:49 +0100
        Re: python 3.3 repr Chris Angelico <rosuav@gmail.com> - 2013-11-16 03:01 +1100
          Re: python 3.3 repr Neil Cerutti <neilc@norwich.edu> - 2013-11-15 17:47 +0000
            Re: python 3.3 repr Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-16 01:09 +0000
      Re: python 3.3 repr Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2013-11-15 17:10 +0000
        Re: python 3.3 repr Chris Angelico <rosuav@gmail.com> - 2013-11-16 04:29 +1100
        Re: python 3.3 repr Cousin Stanley <cousinstanley@gmail.com> - 2013-11-15 10:45 -0700
    Re: python 3.3 repr Joel Goldstick <joel.goldstick@gmail.com> - 2013-11-15 09:50 -0500
    Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 15:03 +0000
    Re: python 3.3 repr Joel Goldstick <joel.goldstick@gmail.com> - 2013-11-15 10:07 -0500
    Re: python 3.3 repr Chris Angelico <rosuav@gmail.com> - 2013-11-16 02:08 +1100
    Re: python 3.3 repr Robin Becker <robin@reportlab.com> - 2013-11-15 15:18 +0000
    Re: python 3.3 repr Roy Smith <roy@panix.com> - 2013-11-15 10:32 -0500
    Re: python 3.3 repr William Ray Wing <wrw@mac.com> - 2013-11-15 11:30 -0500
    Re: python 3.3 repr Zero Piraeus <z@etiol.net> - 2013-11-15 14:06 -0300
    Re: python 3.3 repr Chris Angelico <rosuav@gmail.com> - 2013-11-16 04:11 +1100
    Re: python 3.3 repr Serhiy Storchaka <storchaka@gmail.com> - 2013-11-15 19:37 +0200
  Re: python 3.3 repr Gene Heskett <gheskett@wdtv.com> - 2013-11-15 11:36 -0500
  Re: python 3.3 repr Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-11-15 17:58 +0000
  Re: python 3.3 repr Gene Heskett <gheskett@wdtv.com> - 2013-11-15 14:23 -0500

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