[Python-ideas] Parenthesized Compound With Statement

[Guido van Rossum]

Even though you are responding to my message, you omit what I wrote, and
only weakly support it. So let me repeat: the backslash is the best
solution and te PEP should be amended to prefer it *in this case*.

On Tuesday, July 2, 2013, Andrew Barnert wrote:

> First, you can always do this:
>
>     with open("/long/path/to/file1") as file1, open(
>         "/long/path/to/file2") as file2:
>
> Not exactly beautiful, but perfectly legal and PEP-8-compliant.
>
> Or, of course:
>
>     with open("/long/path/to/file1") as file1:
>         with open("/long/path/to/file2") as file2:
>
> But the best solution is probably:
>
>     path1 = "/long/path/to/file1"
>     path2 = "/long/path/to/file2"
>     with open(path1) as file1, open(path2) as file2:
>
> Meanwhile, PEP 8 doesn't say never to use backslashes no matter what.
> While it says parens "should be used in preference to using a backslash for
> line continuation", it also says, "But most importantly: know when to be
> inconsistent -- sometimes the style guide just doesn't apply. When in
> doubt, use your best judgment." In particular, it specifically says that
> "When applying the rule would make the code less readable, even for someone
> who is used to reading code that follows the rules", you should break it.
>
> So you've got four options in today's language. Is it worth changing the
> syntax to add a fifth?
>
> On Tue, Jul 2, 2013 at 3:37 PM, Matthew Lefavor <mclefavor at gmail.com<javascript:;>>
> wrote:
> >> As you all know, Python supports a compound "with" statement to avoid
> the
> >> necessity of nesting these statements.
> >>
> >> Unfortunately, I find that using this feature often leads to exceeding
> the
> >> 79-character recommendation set forward by PEP 8.
> >>
> >> # The following is over 79 characters
> >> with open("/long/path/to/file1") as file1, open("/long/path/to/file2")
> as
> >> file2:
> >>    pass
> >>
> >> This can be avoided by using the line continuation character, like so:
> >>
> >> with open("/long/path/to/file1") as file1, \
> >>        open("/long/path/to/file2") as file2:
> >>    pass
> >>
> >> But PEP-8 prefers using implicit continuation with parentheses over line
> >> continuation. PEP 328 states that using the line continuation character
> is
> >> "unpalatable", which was the justification for allowing multi-line
> imports
> >> using parentheses:
> >>
> >> from package.subpackage import (UsefulClass1, UsefulClass2,
> >>                                ModuleVariable1, ModuleVariable2)
> >>
> >> Is there a reason we cannot do the same thing with compound with
> statements?
> >> Has this been suggested before? If so, why was it rejected?
> >>
> >> with (open("/long/path/to/file1") as file1,
> >>      open("/long/path/to/file2") as file2):
> >>    pass
> >>
> >> I would be happy to write the PEP for this and get plugged in to the
> Python
> >> development process if this is an idea worth pursuing.
> >>
> >> ML
> >>
> >> _______________________________________________
> >> Python-ideas mailing list
> >> Python-ideas at python.org <javascript:;>
> >> http://mail.python.org/mailman/listinfo/python-ideas
> >
> >
> >
> > --
> > --Guido van Rossum (python.org/~guido)
> > _______________________________________________
> > Python-ideas mailing list
> > Python-ideas at python.org <javascript:;>
> > http://mail.python.org/mailman/listinfo/python-ideas
>


-- 
--Guido van Rossum (on iPad)
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