[Python-Dev] Switch statement (original) (raw)

Fredrik Lundh fredrik at pythonware.com
Fri Jun 23 09:35:19 CEST 2006

Phillip J. Eby wrote:

I think I like it. I was confused by what Fredrik meant by "const", but your renaming it to "static" makes more sense to me;

footnote: I suggested static in my list of use cases; while "const" makes sense in many cases, "static" makes more sense for things like this:

def foo(value): table = const { 1: "one", 2: "two", 3: fie.fum, }

(maybe "static" would be a better keyword?)

...at least for C/C++ heads; if you look things up in a dictionary, I'd say that the noun "constant", in the meaning

2. a. A quantity assumed to have a fixed value in a
      specified mathematical context.
   b. An experimental or theoretical condition, factor,
      or quantity that does not vary or that is regarded
      as invariant in specified circumstances.

makes at least as much sense as the adjective "static":

1. a. Having no motion; being at rest; quiescent.
   b. Fixed; stationary.

Unfortunately this would probably cause people to write

switch x: case static re.DOTALL: ... case static re.IGNORECASE: ... which is just more work to get the same effect as the def-time-switch-freezing proposal. Without the "static", the reordering of execution isn't obvious. But perhaps that could be lived with, if the explanation was, "well, static is implied by case".

I'd still prefer the "explicit is better than implicit" route, approach switch/case (if added) is defined in terms of if/elif, and optimizations are handled by the optimizer/code generator.

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