On Tue, 5 Jul 2005, Mike Cheponis wrote:
> Why does Python not have a "case" statement, like C?
Hi Mike,
It's a proposed enhancement:
http://www.python.org/peps/pep-0275.html
That being said, a dispatch-table approach, using a dictionary, works well
in Python because it's not hard to use functions as values --- most people
haven't really missed case/switch statements in Python because dispatch
tables can be very effective.
For example, something like this:
### C ###
switch(state) {
case STATE_1: doStateOneStuff();
break;
case STATE_2: doStateTwoStuff();
break;
case STATE_3: doStateThreeStuff();
break;
default: doDefaultAction();
######
has a natural translation into Python as:
### Python ###
dispatchTable = { STATE_1: doStateOneStuff,
STATE_2: doStateTwoStuff,
STATE_3: doStateThreeStuff }
command = dispatchTable.get(state, doDefaultAction)
command()
######
where we're essentially mimicking the jump table that a case/switch
statement produces underneath the surface.
One other consideration about C's case/switch statement is its
bug-proneness: it's all too easy to programmers to accidently forget to
put 'break' in appropriate places in there.
Hope this helps!
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