[Python-ideas] More power in list comprehensions with the 'as' keyword

Neil Toronto ntoronto at cs.byu.edu
Thu Aug 28 05:38:35 CEST 2008

Chris Rebert wrote:
> On Wed, Aug 27, 2008 at 4:17 PM, Terry Reedy <tjreedy at udel.edu> wrote:
>> To me, the drive to replace all for loops with list comps is mis-directed.
>>  There is no end to the clauses people could propose to add: while, when,
>> whatever, until, unless. mapped_to, transformed_by, and so on.  The result
>> would soon by something quite different from Python as we know it.
> Indeed, probably something approaching Common Lisp's overcomplicated
> "loop" macro:
> http://www.unixuser.org/~euske/doc/cl/loop.html
> - Chris

Doesn't have to be that bad. I'd personally like a way to make a loop 
expression that returns a list, with two operators that stuff new things 
on and update old ones. That's most likely a reflection of my 
expression-based-but-not-purely style, though.

One thing I've noticed in this discussion is that people seem to want 
the "as" keyword to operate as a general expression-assignment operator. 
Is that worth adding to the language? There would be no possibility of 
getting it mixed up with "==", and the word as an infix operator is 
sufficiently ugly that people would prefer "=" in general.


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