[Tutor] a beginning question

[Peter Otten]

Paul Z wrote:

> Hi,
> 
> I writed some codes as the UDP messages:
> 
> import socket
> import random
> from array import *
> 
> port = 8088
> host = "localhost"
> 
> s = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
> 
> num = array('f')
> x = 0
> while x < 6:
> num.append(random.random())
> x += 1
> 
> a0 = str("%.2f"%num[0]) + ','
> a1 = str("%.2f"%num[1]) + ','
> a2 = str("%.2f"%num[2]) + ','
> a3 = str("%.2f"%num[3]) + ','
> a4 = str("%.2f"%num[4]) + ','
> a5 = str("%.2f"%num[5]) + ','
> 
> msg1 = 'a,' + a0 + a1 + a2
> msg1 = bytes(msg1, 'utf-8')
> msg2 = 'b,' + a3 + a4 + a5
> msg2 = bytes(msg2, 'utf-8')
> 
> s.sendto(msg1, (host, port))
> s.sendto(msg2, (host, port))
> 
> and I receive the messages via:
> 
> import socket
> port = 8088
> s = socket.socket(socket.AF_INET,socket.SOCK_DGRAM)
> s.bind(("",port))
> print('waiting on port:',port)
> while True:
> data,addr = s.recvfrom(1024)
> print('reciveed:', data, "from", addr)
> 
> I want to arrange the messages to:
> 
> array1 = #the numbers which is start as 'a' in the messages
> array2 = #the numbers which is start as b in the messages

You can put the lists into a dict. Then
lists["a"] accesses one and lists["b"] accesses the other list.

items1 = []
items2 = []
lists = {"a": items1, "b": items2}

while True: 
    data, addr = s.recvfrom(1024) 
    print('received:', data, "from", addr)

    parts = data.decode("utf-8").split(",")
    key = parts.pop(0)
    lists[key].extend(float(p) for p in parts if p.strip())

    print("items1:", items1)
    print("items2:", items2)

You can extend this approach to an arbitrary number of lists if you add them 
dynamically to the dict:

lists = {}
while True:
    ...
    parts = ...
    key = parts.pop(0)
    if key not in lists:
        lists[key] = []
    lists[key].extend(...)