Algorithmic complexity of StringIO?

[anton muhin]

Roy Smith wrote:

> I want to build up a long string piece by piece without the quadratic 
> behavior of string concatenation.  I'm looking at the {c,}StringIO 
> modules as a way around this, but I don't see anything in the docs which 
> talks about how they work.  If I do
> 
> s = StringIO.StringIO()
> while whatever:
>    s.write (stringFragment)
> return s.getvalue()
> 
> will I see quadratic behavior?  cStringIO claims to be more efficient, 
> but doesn't say how.  Is it algorithmicly better, or just the same 
> algorithm recoded in C?
> 
> The context here is writing a __str__() method for a container class.  I 
> could envision the containiner holding a couple thousand items, with 
> len(__str__()) being several 10's of kbytes.

Hello, Roy!

Common idiom is to use join method:

bunch_of_strings = ["aaa", ... "zzz"]

result = ''.join(bunch_of_strings)

If I'm correct, join preallocates needed space.

hth,
anton.