[Python-ideas] Dart like multi line strings identation

[MRAB]

On 2018-04-01 20:10, Terry Reedy wrote:
> On 4/1/2018 8:36 AM, Steven D'Aprano wrote:
>> On Sun, Apr 01, 2018 at 08:08:41AM -0400, Richard Damon wrote:
>> 
>>> One comment about the 'combinatorial explosion' is that it sort of assumes
>>> that each individual combination case needs to be handled with distinct
>>> code.
> 
>> No -- as I said in an earlier post, Terry and I (and Eric) are talking
>> about the explosion in number of prefixes, not the complexity of the
>> code.
>> 
>> You are right that many of the prefixes can be handled by the same code:
>> 
>>      rfd rfD rFd rFD rdf rdF rDf rDF
>>      Rfd RfD RFd RFD Rdf RdF RDf RDF
>>      frd frD fRd fRD fdr fdR fDr fDR
>>      Frd FrD FRd FRD Fdr FdR FDr FDR
>>      drf drF dRf dRF dfr dfR dFr dFR
>>      Drf DrF DRf DRF Dfr DfR DFr DFR
>>      # why did we support all these combinations? who uses them?
>> 
>> presumably will all handled by the same "raw dedent f-string" code. But
>> the parser still has to handle all those cases, and so does the person
>> reading the code.
> 
> IDLE's colorizer does its parsing with a giant regex.  The new prefix
> combinations would nearly double the number of alternatives in the
> regex.  I am sure that this would mean more nodes in the compiled
> finite-state machine.  Even though the non-re code of the colorizer
> would not change, I am pretty sure that this would mean that coloring
> takes longer.  Since the colorizer is called with each keystroke*, and
> since other events can be handled between keystrokes#,  colorizing time
> *could* become an issue, especially on older or slower machines than
> mine.  Noticeable delays between keystroke and character appearance on
> screen are a real drag.
> 
In Python 3.7 that part is now:

     stringprefix = r"(?i:\br|u|f|fr|rf|b|br|rb)?"

(which looks slightly wrong to me!).