meta-class review

[Jorgen Grahn]

On Wed, 2010-10-06, Ethan Furman wrote:
> MRAB wrote:
>> On 06/10/2010 00:17, Ethan Furman wrote:
>>  > [snip]
>>  > Any comments appreciated, especially ideas on how to better handle
>>  > class- and staticmethods
>>  >
>> I think that's a bit of overkill. The problem lies in the printing
>> part, but you're spreading the solution into the rest of the
>> application! (A case of the tail wagging the dog, perhaps? :-))
>> 
>> IMHO you should just use a simple function when printing:
>> 
>> def dash_zero(x):
>>     return str(x) if x else '-'
>> 
>> '%-25s: %7s' % ('DPV Failure', dash_zero(counts['D']))
>
> Yes, simple is better than complex, isn't it?  :)  And certainly a *lot* 
> less code!
>
> Thank you for pointing that out -- hopefully my blush of embarassment 
> will fade by morning.

IMHO wrapping it in a class made much sense -- I just didn't see why
it exploded with more and more.  There are a few classes like that which
I frequently use:

a. statistics counters which are like ints, but can only be incremented
   and printed (or placed into SNMP messages, or whatever the system
   uses)

b. integers to be printed right-aligned in tables of a certain width,
   and as '-' or 'n/a' or '' when they are zero.  If they are so
   int-like that you can't do (a), then just build them on-the-fly
   when you're printing:
  
   f.write('%s: %s\n' % (name, MyFormatted(value)))

   Class MyFormatted here is very much like dash_zero above; it
   has no methods except __init__ and __str__.

I mostly do this in C++; perhaps it makes more sense in a language with
static typing, overloading and templates.

/Jorgen

-- 
  // Jorgen Grahn <grahn@  Oo  o.   .  .
\X/     snipabacken.se>   O  o   .