Guido's time machine strikes again, though using a slash (\) rather than elipse:
>>> '.'\ ... .join( ... ( ... '1', ... '2', ... ) ... ) '1.2' This is from Python 2.7.10 (what I have on the machine I am currently on), though I'm fairly sure it has worked for quite a bit longer than that. Chris On Wed, Aug 31, 2016 at 2:46 PM, Shane Hathaway <sh...@hathawaymix.org> wrote: > Hi, > > I write a lot of SQLAlchemy code that looks more or less like this: > > rows = ( > dbsession.query(Table1) > .join( > Table2, Table2.y = Table1.y) > .filter(Table1.x = xx) > .all()) > > The expressions get very long and nearly always need to be spread to > multiple lines. I've tried various styles and have chosen the style above > as the most tasteful available. > > Pros of the existing syntax: > > - It's possible to indent clearly and consistently. > - Nested indentation works out OK. > - It's flexible; I can combine lines or separate them for emphasis. > > Cons: > > - Extra parentheses are required. > - The indentation is not enforced by the parser, so I have unnecessary > freedom that could let various mistakes slip through. > - The closing parenthesis has to move every time I append to or reorder > the expression, leading to diff noise in version control. (Alternatively, I > could put the closing parenthesis on its own line, but that consumes > precious vertical reading space.) > > I'd like to suggest a small change to the Python parser that would make > long expressions read better: > > rows = dbsession.query(Table1) ... > .join( > Table2, Table2.y = Table1.y) > .filter(Table1.x = xx) > .all() > > The idea is to use an ellipsis at the end of a line to spread an > expression over multiple indented lines, terminated by a return to an > earlier indentation level. You can still indent more deeply as needed, as > shown above by the join() method call. > > This syntax has all the pros of the existing syntax and resolves all the > cons: > > - No extra parentheses are required. > - The indentation is enforced, so my mistakes are more likely to be caught > early. > - Without a closing parenthesis, there is no diff noise when I append to > or reorder an expression. > > I've thought about using a colon instead of an ellipsis, but in Python, a > colon starts a list of statements; that's not my goal. Instead, I'm looking > for ways to use parser-enforced indentation to avoid mistakes and help my > code read better without changing any semantics. > > Feedback is welcome! > > Shane > _______________________________________________ > Python-ideas mailing list > Python-ideas@python.org > https://mail.python.org/mailman/listinfo/python-ideas > Code of Conduct: http://python.org/psf/codeofconduct/ >
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