Pass by reference

Chris Rebert clp at
Wed Dec 31 14:29:36 CET 2008

On Wed, Dec 31, 2008 at 5:04 AM, iu2 <israelu at> wrote:
> For the 2 targets I have the variables comm1 and comm2. They are of
> some class I wrote, representing many properties of the communication,
> including the IP address.
> There is one function that sends data, and it receives a commX var
> (comm1 or comm2) as the means for sending the data.
> Before sending the data the function needs to initilze commX (if it is
> still None), or creating it a new, if it sees that the IP for that
> target has changed.

Based on the naming alone (though further corroborated by your
details), I can recommend that you use a dictionary instead of
variables for the commX-s.

Basically, remove the comm1, comm2, etc variables and instead do (you
might want to use a defaultdict or list rather than a plain dict):

comms = {1 : MyComm(...), 2 : None}

> Something like this:
> def send_data(comm, data, current_ip_from_gui):
>  if comm is None:
>    # I want to assign comm a new MyComm
>  elif comm.ip != current_ip_from_gui:
>    # I want to re-assign a new MyComm that uses the new IP
>  comm.socket.SendTo(comm.addr, data)  # eventually send the data

Instead that becomes:

def send_data(comms, id_num, data, current_ip_from_gui):
    if comms[id_num] is None:
        comms[id_num] = MyComm(...)
    elif comms[id_num].ip != current_ip_from_gui:
        comms[id_num] = MyComm(current_ip_from_gui, ...)
    comm = comms[id_num]
    comm.socket.SendTo(comm.addr, data)  # eventually send the data

> But I guess I can achieve this using a class holding my vars, maybe
> like this:

That's similar to what I'm suggesting, but mine has less indirection.


Follow the path of the Iguana...

More information about the Python-list mailing list