And does that remove the need for parentheses? ;) Because actually, it gets more complicated than that. Sometimes it makes more sense to say: def open_wind

And does that remove the need for parentheses? ;) Because actually, it gets more complicated than that. Sometimes it makes more sense to say: def open_window(x, y width, height, resizable=True, caption="") Without parens, is x, y a tuple or two separate arguments? And do I want to remember that? Also, what's inside the parens could have been a generator expression, which could have been conceivably partitioned in more than one sensible way, and which could have subexpressions with parens or brackets itself. Sounds contrived? I do it all the time and it often looks and reads just fine. I'm not arguing against your indentation rule, which is the one I use, and not even against the proposal of making it mandatory (although I'm not sure that in the heat of refactoring I'd appreciate the unnecessary SyntaxErrors), but about the point that making it mandatory would make parens unnecessary.