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List:       python-list
Subject:    Re: map/filter/reduce/lambda opinions and background
From:       "Terry Reedy" <tjreedy () udel ! edu>
Date:       2005-07-09 0:32:08
Message-ID: dan5u9$2df$1 () sea ! gmane ! org
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"George Sakkis" <gsakkis@rutgers.edu> wrote in message 
news:1120852274.923521.211250@g43g2000cwa.googlegroups.com...

> "Steven Bethard" <steven.bethard@gmail.com> wrote:
>> Dict comprehensions were recently rejected:
>>      http://www.python.org/peps/pep-0274.html
>> The reason, of course, is that dict comprehensions don't gain you much
>> at all over the dict() constructor plus a generator expression, e.g.:
>>      dict((i, chr(65+i)) for i in range(4))

> Sure, but the same holds for list comprehensions: list(i*i for i in
> xrange(10)). The difference is historic I guess; list comprehensions
> preceded generator expressions and so they cannot be removed, at least
> not before 3.0. I wonder if they will/should be in the language when
> the constraint of backwards compatibility is lifted.

Guido has asked himself the same question.  Some developers who love l.c.s 
are sure they will stay.  I am not.  I think it might depend on whether 
they have any real advantages in the context of the 3.0 engine and design, 
which don't exist yet.

> IMO they should
> not (TIOOWTDI, uniformity among builtin data structures, not
> overwhelmingly more useful than set or dict comprehensions), but
> there's a long way till that day.

Yes.

Terry J. Reedy



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