list comprehension

[Shalabh Chaturvedi]

Guy Robinson wrote:

> This works I was just wondering if something could be written more 
> concisely and hopefully faster:
> s = "114320,69808 114272,69920 113568,71600 113328,72272"
> e = s.split(' ')
> out =''

outl = []

> for d in e:
>     d =d.split(',')
>     out +='%s,%d ' %(d[0],-int(d[1]))

       outl.append(s) # where s is the string you construct
out = ' '.join(outl)

> print out
> 
> Guy
> 

It's faster to collect strings in a list and join them later than to 
concatenate strings one by one.

Also, do you have to convert d[1] to int? If you are sure that it is 
always a positive integer, you can do  '%s,-%s' % (d[0],d[1]).

In fact you could even try to replace ',' with ',-' instead of splitting 
the string at all. Of course it depends on what the format of your 
incoming string is.

--
Shalabh