[Python-Dev] Wrappers and keywords (original) (raw)

Skip Montanaro skip@pobox.com
Thu, 17 Apr 2003 16:43:23 -0500 

David> It also has the disadvantage of adding a new syntactical
David> construct to the language does it not (which seems like more pain
David> than a couple of keywords)?  I don't recall any other place in
David> the language that uses [] as a way to specify a variable (oops,
David> excepting list comprehensions sort of, and that's not quite the
David> same thing IMO), especially in that position in a statement?

Adding new syntactic sugar is less problem than adding keywords for two reasons:

* old code may have used the new keyword as a variable (because it
  wasn't a keyword)

* old code won't have used the new syntactic sugar (because it wasn't
  proper syntax)

Combined, it means there is a higher probability that old code will continue to run with a new bit of syntax than with a new keyword.

You can think of [mod1, mod2, ...] as precisely a list of modifiers to normal functions, so it is very much like existing list construction syntax in that regard. Also "[...]" often means "optional" in may grammar specifications or documentation, so there's an added hint as to the meaning.

Skip