[Python-Dev] switch-based programming in Python

[M.-A. Lemburg]

Skip Montanaro wrote:
> 
>     >> If you think you need an annotation, you may just as well propose to
>     >> introduce a switch statement into the language.
> 
>     mal> True, but that would probably be even harder to get accepted on
>     mal> python-dev (or would it ;-) ?
> 
>     >> switch x:
>     >>   case 'foo':
>     >>     ...
>     >>   case 'bar':
>     >>     ...
>     >>   case 42:
>     >>     ...
> 
> If you restrict the case values to hashable literals do you need "case"?
> One new keyword would be easier than two for Guido to swallow...
> 
> One other post I saw in this thread used explicit breaks as is required in
> C.  I would get rid of that.  When the current case's code ends, control
> flow should just jump to the end of the switch.  No other block in Python
> falls through like that does it?  Leaving out the break statement can also
> be a subtle source of errors in C code and can probably be eliminated
> without much loss of expressiveness.  Besides, switches (especially those
> used to implement state machines) are often executed inside loops.  If break
> is used to terminate the current case, it's not available to break out of
> the enclosing loop and you're stuck with using a try/except/raise
> combination or setting some state variable and checking it at the bottom of
> each loop.

Very good points ! I think everybody agreed on dropping the 
fallthrough and break idea.

-- 
Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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