[Python-ideas] explicitation lines in python ?

geremy condra debatem1 at gmail.com
Sat Jun 26 08:48:30 CEST 2010

On Fri, Jun 25, 2010 at 11:55 PM, Chris Rebert <pyideas at rebertia.com> wrote:
> On Fri, Jun 25, 2010 at 7:58 PM, Stephen J. Turnbull <stephen at xemacs.org> wrote:
>> Daniel DELAY writes:
>>  > (Sorry if this has already been discussed earlier on this list, I have
>>  > not read all the archives)
>> I think if you search for "first-class blocks" and "lambdas", or
>> similar, you'll find related discussion (although not exactly the same
>> thing).  It also looks very similar to the Haskell "where", maybe
>> searching for "Haskell where" would bring it up.
>>  > Renouncing to list comprehension occurs rather often when I write python
>>  > code
>>  >
>>  > I think we could greatly improve readability if we could keep list
>>  > comprehension anywhere in all cases, but when necessary explicit a too
>>  > complex expression in an indented line :
>>  >
>>  > htmltable = ''.join( '<tr>{}</tr>'.format(htmlline) for line in table):
>>  >     htmlline : ''.join( '<td>{}</td>'.format(cell) for cell in line)
>> (Edited for readability; it was munged by your mail client. ;-)
>> I'm not sure I like this better than the alternative of rewriting the
>> outer loops explicitly.  But if you're going to add syntax, I think
>> the more verbose
>>    htmltable = ''.join('<tr>{}</tr>'.format(htmlline) for line in table) \
>>        with htmlline = ''.join('<td>{}</td>'.format(cell) for cell in line)
>> looks better.  Note that the "with" clause becomes an optional part of
>> an assignment statement rather than a suite controlled by the
>> assignment, and the indentation is decorative rather than syntactic.
>> I considered "as" instead of "=" in the with clause, but preferred the
>> "=" because that allows nested "with" in a natural way.  (Maybe, I
>> haven't thought carefully about that at all.)  Obviously "with" was
>> chosen because it's already a keyword.
>> I suspect this has been shot down before, though.
> Prior thread:
> [Python-ideas] Where-statement (Proposal for function expressions)
> http://mail.python.org/pipermail/python-ideas/2009-July/005114.html

I was all set to dislike this syntax, but after reading over it a bit I
find myself liking it a lot. Was the code for this (or similar) ever
written, or was it just proposed?

Geremy Condra

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