python - tkinter root.mainloop with While True loop

Question

I am using tkinter to display some labels based on voltages I am reading. However, it stops executing after one read. I have found that it is due to root.mainloop(). But I am not able to fix it. I have included my code. The root.mainloop() is located right at the end of the while True.

from Tkinter import *
import spidev
import time
import os
import RPi.GPIO as GPIO
import numpy

GPIO.cleanup()
GPIO.setmode(GPIO.BOARD)
GPIO.setup(7, GPIO.OUT)
GPIO.setup(11, GPIO.OUT)
GPIO.setup(13, GPIO.OUT)
GPIO.setup(15, GPIO.OUT)
GPIO.setup(12, GPIO.OUT)
adcvolt = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]
batvolt = [0,0,0,0,0,0,0,0,0,0,0,0,0,0,0]

root = Tk() #Makes the window
w,h = root.winfo_screenwidth(), root.winfo_screenheight()
root.overrideredirect(1)
root.geometry("%dx%d+0+0"%(w,h))

labelFont = ("times",15 ,"bold", "italic")
labelText1 = StringVar()
labelText2 = StringVar()
labelText3 = StringVar()
labelText4 = StringVar()
labelText5 = StringVar()
labelText6 = StringVar()

labelText1.set("Battery Management System")
label1 = Label(root, textvariable=labelText1, height=3, anchor="center")
label1.config(font=labelFont)
label1.pack()
labelText2.set("Wait")
label2 = Label(root, textvariable=labelText2, height=3, anchor="center")
label2.config(font=labelFont)
label2.pack()
labelText3.set("Wait")
label3 = Label(root, textvariable=labelText3, height=3, anchor="center")
label3.config(font=labelFont)
label3.pack()
labelText4.set("Wait")
label4 = Label(root, textvariable=labelText4, height=3, anchor="center")
label4.config(font=labelFont)
label4.pack()
labelText5.set("Wait")
label5 = Label(root, textvariable=labelText5, height=3, anchor="center")
label5.config(font=labelFont)
label5.pack()
labelText6.set("Wait")
label6 = Label(root, textvariable=labelText6, height=3, anchor="center")
label6.config(font=labelFont)
label6.pack()
#root.wm_title("Window Title") #Makes the title that will appear in the top left
#root.config(background = "#FFFFFF") #sets background color to white


# Open SPI bus
spi = spidev.SpiDev()
spi.open(0,0)

# Function to read SPI data from MCP3008 chip
# Channel must be an integer 0-7
def ReadChannel(channel):
  adc = spi.xfer2([1,(8+channel)<<4,0])
  data = ((adc[1]&3) << 8) + adc[2]
  return data

#Function to select multiplexer channel on 74HCT4067 chip
#Channel must be an integer 0-15
def MuxSelect(muxchannel):
    if muxchannel == 0:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 1:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 2:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 3:
        GPIO.output(7,0)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 4:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 5:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 6:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 7:
        GPIO.output(7,0)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 8:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 9:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 10:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 11:
        GPIO.output(7,1)
        GPIO.output(11,0)
        GPIO.output(13,1)
        GPIO.output(15,1)
    elif muxchannel == 12:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,0)
    elif muxchannel == 13:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,0)
        GPIO.output(15,1)
    elif muxchannel == 14:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,0)
    elif muxchannel == 15:
        GPIO.output(7,1)
        GPIO.output(11,1)
        GPIO.output(13,1)
        GPIO.output(15,1)



# Function to convert data to voltage level,
# rounded to specified number of decimal places. 
def ConvertVolts(data,places):
  volts = (data * 3.3) / 1023
  volts = round(volts,places)
  return volts

# Define sensor channels
voltage_channel = 0


# Define delay between readings
delay = 2




while True:
  count = 0

  while count<15:
    MuxSelect(count)

    # Read the voltage sensor data
    voltage_level = ReadChannel(voltage_channel)
    voltage_volts = ConvertVolts(voltage_level,2)
    adcvolt[count] = voltage_volts
    batvolt[count] = adcvolt[count] * 2.842

    #print adcvolt[count]
    #print batvolt[count]
    #print count
    count = count + 1
    #time.sleep(delay)
  labelText2.set('Cell1= '+str(batvolt[0])+'V  Cell2= ' +str(batvolt[1])+'V  Cell3= '+str(batvolt[2]))
  #root.update()
  labelText3.set('Cell4= '+str(batvolt[3])+'V  Cell5= ' +str(batvolt[4])+'V  Cell6= '+str(batvolt[5]))
 # root.update()
  labelText4.set('Cell7= '+str(batvolt[6])+'V  Cell8= ' +str(batvolt[7])+'V  Cell9= '+str(batvolt[8]))
#  root.update()
  labelText5.set('Cell10= '+str(batvolt[9])+'V  Cell11= ' +str(batvolt[10])+'V  Cell12= '+str(batvolt[11]))
#  root.update()
  labelText6.set('Cell13= '+str(batvolt[12])+'V  Cell14= ' +str(batvolt[13])+'V  Cell15= '+str(batvolt[14]))
  root.update()
  print "shit"  

  medianvolt = numpy.median(batvolt)
  maxvolt = max(batvolt)
  minvolt = min(batvolt)
  diff1 = maxvolt-medianvolt
  diff2 = medianvolt-minvolt

  if diff1>0.02 or diff2>0.02:
    GPIO.output (12,1)
    time.sleep(120)
    GPIO.output (12,0)


    # Wait before repeating loop
    time.sleep(delay)

  root.update()

  root.mainloop() #start monitoring and updating the GUI. Nothing below here runs.

Answer 1

Tkinter needs mainloop to work (to call all functions behind).
Use root.after(time_ms, function_name_without_() ) (before mainloop)
to run some function - and that function have to run the same after(...) to work in loop.

In Tkinter you don't use while True because while True is to make (main)loop
but Tkinter has own mainloop.

And don't use sleep() - use after()

Put all code from while True (except mainloop) in some function and call it using after().
Use second after() in place of sleep().

import Tkinter as tk

master = tk.Tk()

def my_mainloop():
    print "Hello World!"
    master.after(1000, my_mainloop)    

master.after(1000, my_mainloop)

master.mainloop()