Receive data from socket stream

[Nick Craig-Wood]

Hrvoje Niksic <hniksic at xemacs.org> wrote:
>  Nick Craig-Wood <nick at craig-wood.com> writes:
> 
> > What you are missing is that if the recv ever returns no bytes at all
> > then the other end has closed the connection.  So something like this
> > is the correct thing to write :-
> >
> >   data = ""
> >   while True:
> >       new = client.recv(256)
> >       if not new:
> >           break
> >       data += new
> 
>  This is a good case for the iter() function:
> 
>  buf = cStringIO.StringIO()
>  for new in iter(partial(client.recv, 256), ''):
>      buf.write(new)
>  data = buf.getvalue()
> 
>  Note that appending to a string is almost never a good idea, since it
>  can result in quadratic allocation.

My aim was clear exposition rather than the ultimate performance!

Anyway str += was optimised in python 2.4 or 2.5 (forget which) wasn't
it?  I'm not convinced it will be any worse performing than
cStringIO.StringIO.write() which effectively appends to a string in
exactly the same way.

This test agrees with me!

$ python -m timeit -s 's = ""' 'for i in xrange(100000): s+="x"'
10 loops, best of 3: 23.8 msec per loop

$ python -m timeit -s 'from cStringIO import StringIO; s=StringIO()' 'for i in xrange(100000): s.write("x")'
10 loops, best of 3: 56 msec per loop

-- 
Nick Craig-Wood <nick at craig-wood.com> -- http://www.craig-wood.com/nick