Speeding up: s += "string"

[Jp Calderone]

On Thu, May 08, 2003 at 02:47:08PM -0700, Erik Max Francis wrote:
> Beat Bolli wrote:
> 
> > When I'm really concerned about speed, I pre-bind the append method:
> > 
> >      lst = []
> >      add = lst.append
> >      for many times:
> >          add(stuff)
> >      return ''.join(lst)
> > 
> > You could also define a global concat function:
> > 
> >      concat = ''.join
> > 
> > and use this in the last line above.
> 
> The expense here is not in the calling of the function, it's in the time
> it takes the function to run.  Repeatedly using

  Creating and calling a bound method object is expensive too (about 30%
more expensive than calling a regular function, iirc).  Beat Bolli's
solution moves this overhead outside the loop, instead of having Python
create a new bound method object for every iteration.

  It can yield noticable speedups, and I've used it myself here and there.

  Jp

-- 
A disciple of another sect once came to Drescher as he was eating his
morning meal. "I would like to give you this personality test," said the
outsider, "because I want you to be happy." Drescher took the paper that was
offered him and put it into the toaster: "I wish the toaster to be happy, 
too."
-- 
 up 7 days, 16:38, 8 users, load average: 0.00, 0.00, 0.00