REALLY need help with iterating a list.
This has been driving me buggy for 2 days, i need to be able to
iterate a list of items until none are left, without regard to which
items are removed. I'll put the relevant portions of code below,
please forgive my attrocious naming conventions.
Basically i'm trying to spin up some subprocesses that will ping a
group of servers and then wait until all of them have completed (good
or bad), store the ping result and the return code, and move on.
The problem comes in the second block, when i try to iterate the
list of servers and remove the ones that are finished, for some reason
Python appears to re-index the list when I remove an item and the next
step through the loop it cant find the item its expecting because the
indexes have changed.
Any assistance would be appreciated...
=
for server in serverlist:
ping[server] = subprocess.Popen("ping -c 1 " + str(server) + " 5",
shell=True, stdout=subprocess.PIPE)
while len(serverlist) > 0:
for server in serverlist:
if ping[server].returncode==None:
ping[server].poll()
else:
pingresult[server] = ping[server].stdout.read()
pingreturncode[server] = ping[server].returncode
serverlist.remove(server)
--
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Re: REALLY need help with iterating a list.
On Jun 11, 1:23 pm, Fredrik Lundh <[EMAIL PROTECTED]> wrote: > infidel wrote: > > How about something like this? > > > while serverlist: > > server = serverlist.pop(0) > > pinger = ping[server] > > if pinger.returncode==None: > > pinger.poll() > > serverlist.append(server) > > else: > > pingresult[server] = pinger.stdout.read() > > pingreturncode[server] = pinger.returncode > > > Basic idea: as long as there are servers in the list, pop the first > > one out of the list, see if it's done, and if it isn't, put it back on > > the end of the list. > > here's a simple variation of that, which is a bit more efficient, and > perhaps also a bit easier to use in the general case: > > while serverlist: > still_active = [] > for server in serverlist: > pinger = ping[server] > if pinger.returncode is None: > pinger.poll() > still_active.append(server) > else: > pingresult[server] = pinger.stdout.read() > pingreturncode[server] = pinger.returncode > serverlist = still_active > > Thats an interesting approach but, if the returncode for a given server is None say, 20 times in a row you will have append'ed that server to the list 20 times, i suppose you could check the list to see if its already there but thats a bit kludgey... also, the line "pinger = ping[server]" would have to be extracted from this loop otherwise your going to ping the same server repeatedly until it answers... -- http://mail.python.org/mailman/listinfo/python-list
Re: REALLY need help with iterating a list.
On Jun 11, 12:59 pm, infidel <[EMAIL PROTECTED]> wrote:
> On Jun 11, 11:30 am, Radamand <[EMAIL PROTECTED]> wrote:
>
>
>
> > This has been driving me buggy for 2 days, i need to be able to
> > iterate a list of items until none are left, without regard to which
> > items are removed. I'll put the relevant portions of code below,
> > please forgive my attrocious naming conventions.
> > Basically i'm trying to spin up some subprocesses that will ping a
> > group of servers and then wait until all of them have completed (good
> > or bad), store the ping result and the return code, and move on.
> > The problem comes in the second block, when i try to iterate the
> > list of servers and remove the ones that are finished, for some reason
> > Python appears to re-index the list when I remove an item and the next
> > step through the loop it cant find the item its expecting because the
> > indexes have changed.
> > Any assistance would be appreciated...
>
> > =
> > for server in serverlist:
> > ping[server] = subprocess.Popen("ping -c 1 " + str(server) + " 5",
> > shell=True, stdout=subprocess.PIPE)
>
> > while len(serverlist) > 0:
> > for server in serverlist:
> > if ping[server].returncode==None:
> > ping[server].poll()
> > else:
> > pingresult[server] = ping[server].stdout.read()
> > pingreturncode[server] = ping[server].returncode
> > serverlist.remove(server)
>
> How about something like this?
>
> while serverlist:
> server = serverlist.pop(0)
> pinger = ping[server]
> if pinger.returncode==None:
> pinger.poll()
> serverlist.append(server)
> else:
> pingresult[server] = pinger.stdout.read()
> pingreturncode[server] = pinger.returncode
>
> Basic idea: as long as there are servers in the list, pop the first
> one out of the list, see if it's done, and if it isn't, put it back on
> the end of the list.
I like this idea, ill try it out asap.
ok, tried it, works perfectly!! It never occurred to me to use pop to
pull one off and put it back on if it wasnt done, very nice! Thank
You!!
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