case do problem

MRAB python at mrabarnett.plus.com
Tue Mar 2 19:26:08 CET 2010


Tracubik wrote:
> hi, i've to convert from Pascal this code:
> 
> iterations=0;
> count=0;
> REPEAT;
>   iterations = iterations+1;
>   ...
>   IF (genericCondition) THEN count=count+1;
>   ...
>   CASE count OF:
> 	1: m = 1
>         2: m = 10
>         3: m = 100
> UNTIL count = 4 OR iterations = 20
> 
> i do something like this:
> 
> iterations = 0
> count = 0
> 
> m_Switch = (1,10,100)
> 
> while True:
> 	iterations +=1
> 	...
> 	if (genericCondition):
> 		count +=1
> 	...
> 	try:
> 		m = m_Switch[count-1]
> 	except: pass
> 	if count = 4 or iterations = 20
> 
> the problem is that when count = 4 m_Switch[4-1] have no value, so i use 
> the try..except.
> 
> Is there a better solution to solve this problem? and, generally 
> speaking, the try..except block slow down the execution of the program or 
> not?
> 
Use a dict:

     m_Switch = {1: 1, 2: 10, 3: 100}

and then catch the KeyError.

Don't use a bare 'except', catch the specific exception you want to
catch, and don't worry about the speed unless you discover that it's
real problem.



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