Integrating serial communication in wx GUI - user-interface

Question

def updateV(self, event):
""""""
global v
v=random.uniform(1,10)
print('battery voltage =')
print(v)
if v>3:
self.labelOne.SetBackgroundColour('red')
self.labelOne.SetLabel('Battery Voltage : ' + str(v))
else:
self.labelOne.SetBackgroundColour('white')
self.labelOne.SetLabel('Battery Voltage : ' + str(v))
self.Refresh()
this is a function in my wxpython GUI which i use for generating random values.I have added this function in my panel class of the GUI. I have put a wx.Bind function that assigns a timer value to it and refreshes it regularly for value change regularly.
Now the GUI needs to have serial communication as I need to get sensor values and get them input in my GUI screen. So i found this code for serially inputing the value:
def updateV(self, event):
""""""
global v
v=ser.readline()
print v
if v>3:
self.labelOne.SetBackgroundColour('red')
self.labelOne.SetLabel('Battery Voltage : ' + str(v))
else:
self.labelOne.SetBackgroundColour('white')
self.labelOne.SetLabel('Battery Voltage : ' + str(v))
self.Refresh()
I then went it the init part of the panel class and added this code:
ser = serial.Serial('COM3', 9600, timeout=0)
On running the GUI, the value doesnt appear nor does it print it on the GUI. I know I am doing a big mistake here. Anyways the values right now come through an arduino uno connected to a XBEE shield which receives 1-20 values through another arduino conencted to a XBEE shield. By the way, random variables are generated properly and are printed in the GUI so there is'nt any proble with the function.
I need a way for python to read the value serially and assign it to a variable such that I can print the value I get in my GUI screen.
PS: I used the same serial code to properly get 0 1 2 3 4 5 6 7 8 9 10 value on the command screen of python module.
import serial
import time
ser = serial.Serial('COM3', 9600, timeout=0)
while 1:
v=ser.readline()
print v
time.sleep(1)
I am trying to get used to python, but these small things hinder my progress.. I am new to python, please bear with me!

Answer 1

Your problem is essentially that reading the serial interface in the while loop with ser.readline() as in your last example (EDIT1: and also when polling with a wx.Timer event) will block the GUI when it is waiting for data on the serial interface. Calling the app.MainLoop() will loop the wxPython event system. However, the only thing your GUI example will do is blocking at ser.readline(). As soon some data comes it will continue in the updateV method. But because the next timer event is waiting already, it will run to ser.readline() and block there again and preventing any GUI updates.
Did you try out the wxTerminal example in the pyserial package?
It shows how to spin of a thread which will do the reading and sending a user-defined SerialRxEvent so that everything is thread-safe.
You also should read LongRunningTasks in the wxPython wiki to get an idea how to use threads for long running/blocking tasks in wxPython and communicate back to the main GUI thread safely.