Python list populate, and remove item in while loop

Question

I am receiving ID's from a transmission, from different devices. I am placing those ID's into a list with a while. Populating the list is easy, but I would like to set a timer for if one of the transmitters stops transmitting for a time x, I would like to remove that ID from the list.

To build this list I have:

tags_list = []

    while True:
    #######################################################################################
    #FOR CHECK IN THREAD
    #######################################################################################     

    readable, writable, exceptional = select.select([sock], [], [], 1.0)
    if readable:
        data = sock.recv(1024)
        tag_address = ':'.join('%02x' % ord(c) for c in data[12:6:-1])          
        if len(data) == 41:
            if tag_address in valid_tags:
                if len(tags_list) > 0:
                    if tag_address not in wander_tags:
                            tags_list.append(tag_address)
                else:
                    print "ERROR"

But I cannot come up with a way to effectively remove an ID from the list when it is not received. Any ideas? tag_address is formatted xx:xx:xx:xx:xx:xx

Edited to remove "list" as name of the list.

Answer 1

Without seeing the rest of your code all I could say is you need to keep track of the last transmission time/ID somewhere, make a copy of list (it's bad idea to remove things form a sequence you are currently iterating over) excluding any elements where time_now - last_transmission_time > timeout_value and then replace list with the copy.

So something like:

def clean_list(lst):
    return [ele for ele in lst if ele.last_transmission - time_now < timeout_value]

while True:
    ID = data[1:4]      
    if ID not in id_list:
       id_list.append(ID)
    id_list = clean_list(id_list)

I'm using dot notation for clarity and ease of use but you would have to make this work for your setup.

Answer 2

I'd use a dict.

import time

transmitted_IDs = {}
while True:     
    to_delete = []
    ID = data[1:4]      
        if ID not in transmitted_IDs:
            transmitted_IDs[ID] = time.time()
    for ID, time_taken in transmitted_IDs.iteritems():
        ## Iterating over a dict, we get key, value pairs
        ## So here time_taken is transmitted_IDs[ID] 
        if time.time() - time_taken >= x:
            to_delete.append[ID]
    for ID in to_delete:
        del transmitted_IDs[ID]

You can use transmitted_IDs.keys() instead of wherever you're using list in other places in the code now.