[Python-Dev] Why both r'' and R'', u'' and U''?

[M.-A. Lemburg]

Ka-Ping Yee wrote:
> 
> Sorry i'm being forgetful -- could someone please refresh my memory:
> 
> Was there a good reason for allowing both lowercase and capital 'r'
> as a prefix for raw-strings?  I assume that the availability of both
> r'' and R'' is what led to having both u'' and U''. 

Right.

> Is there any
> good reason for that either?

No idea... I have never used anything other than the lowercase
versions.
 
> This just seems to lead to ambiguity and unneeded complexity:
> more cases in tokenize.py, more cases in tokenize.c, more work
> for IDLE, more annoying when searching for u' in your editor.
> (I was about to fix the lack of u'' support in tokenize.py and
> that made me think about this.)
> 
> What happened to TOOWTDI?
> 
> Would you believe we now have 36 different ways of starting a string:
> 
>     '      "      '''    """
>     r'     r"     r'''   r"""
>     u'     u"     u'''   u"""
>     ur'    ur"    ur'''  ur"""
>     R'     R"     R'''   R"""
>     U'     U"     U'''   U"""
>     uR'    uR"    uR'''  uR"""
>     Ur'    Ur"    Ur'''  Ur"""
>     UR'    UR"    UR'''  UR"""
>
> Would it be outrageous to suggest deprecating the last five rows?

No. + 1 on the idea.
 
> -- ?!ng
> 
> [1] We started with 4.  Perl has (by my count) 381 ways of starting
>     a string literal, so we're halfway there, logarithmically speaking.
>     Perl has 757 if you count the fancier operators qx, qw, s, and tr.
> 
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-- 
Marc-Andre Lemburg
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