Re: Receive data from socket stream
On Mon, 28 Apr 2008 08:30:03 -0500, Nick Craig-Wood <nick@xxxxxxxxxxxxxx> wrote:
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
It's a bit nice that using cStringIO doesn't rely on a very esoteric
optimization in the CPython eval loop, as well as on what references
happen to exist to what objects. For example, one might want to use a
debugger without falling back to the quadratic behavior of repeated
string concatenation. cStringIO wins out in this case.
Jean-Paul
.
Relevant Pages
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(comp.lang.vhdl) - extension_pack
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(comp.lang.vhdl) - extension_pack
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(comp.lang.vhdl) - extension_pack
... It is used to set upper loop -- limits for non-deterministic values thus avoiding the use of access -- types and enabling the functions to be used for synthesizeable code. ... DivisorVal: integer) return std_logic_vector; function "/"(DividendVal: string; DivisorVal: integer) return std_logic_vector; ... for loopVar in 0 to slvVal'length/4-1 loop ... end loop; if then return not resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to else return resultVar; -- "width mismatch" errors here are due to improper sizing of the vector that this function is assigned to end if; ...
(comp.lang.vhdl) - Re: Letter to US Sen. Byron Dorgan re unpaid overtime
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