Re: Receive data from socket stream

Hrvoje Niksic <hniksic@xxxxxxxxxx> wrote:
Nick Craig-Wood <nick@xxxxxxxxxxxxxx> 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@xxxxxxxxxxxxxx> -- http://www.craig-wood.com/nick
.

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