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[Python-Dev] Re: Update PEP 292

Brett C. bac at OCF.Berkeley.EDU
Fri Aug 20 01:12:54 CEST 2004 
Barry Warsaw wrote:

> On Thu, 2004-08-12 at 01:19, Tim Peters wrote:
> 
> 
>>I do object to this part:
>>
>>     If the $ character appears at the end of the line, or is followed
>>     by any other character than those described above, it is treated
>>     as if it had been escaped, appearing in the resulting string
>>     unchanged.
>>
>>There's already a facility to escape $, and it's dead easy to use.  $
>>isn't a frequently needed character either in most apps.  So escaping
>>$ "by magic" too is, I think, more likely to make typing errors harder
>>to find than to do anyone real good.
> 
> 
> What would you do about $'s at the end of the string?  I think the
> implementation would be much more complex if you didn't have this rule,
> e.g. you'd have to match \$$ and the $-placeholder regexps would
> basically have to match everything.  Then the .sub call would have to be
> more complex too, because it would have to check for the existence of
> those match groups and then raise an exception.  Or something like that.
> 

Got an implementation and it's simple.  =)  It only required one 
additional group at the end (r"(?<!\$)(\$)$") in the regex and a test if 
it matched.

I tested against "$$" to be fine but for "blah $" and "$" to raise an 
exception.  Those all work and the tests in test_pep292 all pass.

If Barry is okay with this I can apply the patch and update the tests 
and the PEP.  Do need to know what exception to raise when this does 
occur, though.  ValueError?

-Brett
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