On Wed, 23 Jun 2010 04:47:47 pm Alan Gauld wrote: > "Mark Young" <marky1...@gmail.com> wrote > > > I searched the internet, and found someone suggest adding spaces > > after each > > number, which indeed works properly. > > > >>>> answer = 6 .__sub__(7 .__neg__()) > >>>> answer > > > > 13 > > > > Why does this work? I don't even understand why python recognizes > > that I'm > > trying to access the numbers' __sub__ and __neg__ methods, I would > > think > > that the spaces would cause it to not work, but obviously it works > > just > > fine. > > I assume that's a hard coded hack in python to avoid some ambiguity > with decimal points. But I'm not sure.
No, it seems to be by design of the syntax: whitespace within an expression always separates tokens, and you can use as much of it, or as little, as you like: >>> "abc" . upper () + "XYZ".lower() 'ABCxyz' >>> [ 2 , 3 , 4 ] +[5,6,7] [2, 3, 4, 5, 6, 7] The only time when you *must* use whitespace between tokens is to avoid ambiguity, e.g. around the `is` operator, or when using dot method access on a literal int or float. I'm sure this wasn't added to Python specifically to allow calling methods on numeric literals. You can use parentheses for that: >>> (1).__str__() '1' This will be a side-effect of the fact that you can always add a space around tokens and have them still work fine. -- Steven D'Aprano _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
