String concatenation

[Dave Benjamin]

In article <7xr7v5fm3o.fsf at ruckus.brouhaha.com>, Paul Rubin wrote:
> "Leif B. Kristensen" <junkmail at solumslekt.org> writes:
>> >   tmp = [x for x in res if x and x[0] != '-']
>> >   return ', '.join(tmp)
>> 
>> Substituting tmp with the real thing, it turns into a one-liner:
>> 
>> return ', '.join([x for x in res if x and x[0] != '-'])
>> 
>> Awesome :-)
> 
> Yeah, I wrote it that way at first, but figured it was obscure enough
> already if you weren't used to list comprehensions, so I put back the
> tmp variable.

FWIW, I'm used to seeing (and writing) stuff like this, and I don't think
the "tmp" adds any clarity. You could wrap around it with a function,
though, if you needed it often enough:

def join_if(pred, seq, sep):
    return sep.join([x for x in seq if pred(x)])

def valid(x):
    return x and x[0] != '-'
    
return join_if(valid, res, ', ')

-- 
.:[ dave benjamin: ramen/[sp00] -:- spoomusic.com -:- ramenfest.com ]:.
:  please talk to your son or daughter about parametric polymorphism. :