Is it possible to make multiple instances of serial.Serial() in pyserial?

Question

The function I am trying to create finds the port of a modem in charge of AT commands. I am trying to make different instances of serial.Serial() to be local to different loops. I looked in the documentation I could find for info, but none of the ones I found mentioned this in any way (if it is somewhere and I missed it, please feel free to make me look stupid and link it). For example:

    OpenPorts = []
    j=[]
    for modem in PortList:          #This opens every Modem
            for port in modem:
                    try:
                            j=[]
                            print port
                            ser = serial.Serial(port, 9600, timeout=1)
                            ser.close()
                            ser.open()
                            j.append(port)
                    except serial.SerialException:
                            continue
            OpenPorts.append(j) 
            print OpenPorts
    del j
    del ser

That works. But when I try this:

 for port in OpenPorts:
            if port is not '':
                    ser = serial.Serial(port, 9600, timeout=1) 
                    ser.write('ati')
 del ser

I get 'TypeError: can only concatenate list (not "int") to list'

I need to keep them local to the loops because I am opening multiple ports from a set list of ports in use (collected from another file). I have to use multiple loops because I need to use time.sleep() before ser.read() will return anything. Is there any way of doing it in this way, or is it back to the drawing board?

Answer 1

instead of storing the port:

j.append(port)

Why don't you append the ser instance so you can later use like this:

j.append(ser)

for ser in OpenPorts:
       ser.write('ati')

and the later you can close them all with :

for ser in OpenPorts:
       ser.close()