[Python-ideas] Fwd: Add Unicode-aware str.reverse() function?

Chris Angelico rosuav at gmail.com
Sat Sep 8 15:19:31 EDT 2018

On Sat, Sep 8, 2018 at 11:41 PM, Jonathan Fine <jfine2358 at gmail.com> wrote:
> M.-A. Lemburg wrote:
>> Most likely yes, but they would not render RTL text by first
>> switching the direction and then printing them LTR again.
>> Please also note that switching from LTR to RTL and back again
>> is possible within a Unicode string, so applying str.reverse()
>> would actually make things worse and not better :-)
>> Processing in Unicode is always left to right, even if the resulting
>> text may actually be rendered right to left or top to bottom.
>> http://www.unicode.org/reports/tr9/
>> https://www.w3.org/International/questions/qa-scripts
> Your reminder of the difficulties in Unicode, and the URLs are much
> appreciated. In particular, the keyword 'while' in Arabic should be
> written Left-To-Right, even though the ambient text is Left-To-Right.
> I've found these URLs, which suggests that there's a still a problem
> to be solved.
> https://www.linkedin.com/pulse/fix-rtl-right-left-support-persian-arabic-text-ubuntu-ghorbani/
> https://askubuntu.com/questions/983480/showing-text-file-content-right-to-left-in-the-terminal
> https://github.com/behdad/bicon
> My understanding is that at present it's not straightforward to
> provide legible localised text at the Python console, when the locale
> language is Arabic, Persian, Hebrew or Urdu. (And another problem is
> allow copy and paste of such text.)
> If it is straightforward to provide RTL localisation at the Python
> interpreter, I'd very much appreciate being pointed to such a
> solution.

Generally, problems with RTL text are *display* problems, and are not
solved by reversing strings. I've hardly ever needed to reverse a
string, and when it does happen, it's generally for the sake of
*parsing*. You reverse a string, parse it from left to right, then
reverse the result, in order to do a "parse from the right" operation.
Never done that in Python, because the situations where that's
necessary are (a) rare, and (b) generally suitable for a regex anyway.
Does anyone have a really complex parsing job that absolutely cannot
be done with a regex, and benefits from reversal?


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