Creating a UI for another Python program. How do I make a printing label in tkinter for Python 3?

Question

I am creating a UI for another python program and it essentially just makes an interactive component to the project. The goal is to have a specific label that updates (print statements) from the python program the button runs. This is what I have programmed in my UI...

---

import tkinter as ttk
import subprocess
import sys
import time
import os
import tkinter.font as font
from tkinter.ttk import *

app = ttk.Tk()

app.geometry("400x400")
app.configure(bg='gray')

photo = ttk.PhotoImage(file=r"C:\Users\ex\ex_button_active.png")
myFont = font.Font(family='Helvetica', size=20, weight='normal')

ttk.Label(app, text='Ex', bg='gray', font=(
    'Verdana', 15)).pack(side=ttk.TOP, pady=10)
app.iconbitmap(r'C:\Users\ex\ex_icon.ico')


def ex_activation():
    global pro
    print("Running program!")
    pro = subprocess.Popen("python programex.py", shell=True)


def ex_stop():
    global pro
    print("Stopping Program... Please Wait!")
    os.kill(pro.pid, 0)


ex_activation_button = ttk.Button(app, bg='black', image=photo, width=120, height=120, command=ex_activation)

ex_stop_button = ttk.Button(app, bg='Gray', text='Stop Program', width=12, command=ex_stop, height=3)

ex_stop_button['font'] = myFont

app.title("Ex")
ex_activation_button.pack(side=ttk.TOP)
ex_stop_button.pack(side=ttk.LEFT)

# app.mainloop()
while True:
    try:
        app.update()
        app.update_idletasks()
    except KeyboardInterrupt:
        pass

---

If anyone has an idea of how I can implement This StackOverflow Post into my code, I would greatly appreciate the help and support.

EDIT for acw1668 These are some tests I had run and got some strange numbers in the Pycharm run window instead of the UI.

Running program!
3528
Stopping Program 3528 ... Please Wait!
monitor done
Running program!
144
Stopping Program 144 ... Please Wait!
monitor done
Running program!
14008
Stopping Program 14008 ... Please Wait!
monitor done
Running program!
21748
Stopping Program 21748 ... Please Wait!
monitor done

Answer 1

I used a simplified version of your code. To get the print status inside the tkinter app, the easiest way I have thinked of is using a third file: in my case, log.txt.

The daemon.py will log() some output (custom function) to the text file instead of printing it. And in the tkinter mainloop, the app will be constantly checking changes to that file.

Note that with file.readline(), I am just reading one line, as tkinter Labels prefer that. If you plan using more lines, you could change the label to a textarea.

Anyway: here is the code. I hope it'll work inside your project!

# FILE 1: daemon.py

from time import sleep
from sys import exit

def log(s): # This will be the equivalent to the print function
    with open("log.txt", "w") as fileout:
        fileout.write(s)

x = 0
while True:
    try:
        log("seconds elapsed: " + str(x))
        x+=1
        sleep(1)
    except KeyboardInterrupt:
        log("Stopping with x =" + str(x))
        exit()

# FILE 2: log.txt

# You can leave this file empty, but you must create a file named 'log.txt'.

# FILE 3: mainapp.py

import tkinter as tk
import subprocess
import os

def ex_activation():
    print("Running")
    global pro
    pro = subprocess.Popen("python daemon.py", shell=True)

def ex_stop():
    print("Stopped") # I just dont know why, but this print can't be removed.
    global pro
    os.kill(pro.pid, 0)

app = tk.Tk()

ex_activation_button = tk.Button(app, text="run", command=ex_activation)
ex_stop_button = tk.Button(app, text="stop", command=ex_stop)
lab = tk.Label(app, text="If you see this, an error occurred")

with open("log.txt", "w+") as fileinout:
    fileinout.write("Click run to start the execution!")
    lab.config(text=fileinout.readline())

ex_activation_button.pack()
ex_stop_button.pack()
lab.pack()

# app mainloop
while True:
    try:
        app.update()
        app.update_idletasks()
        with open( "log.txt", "r" ) as filein:
            lab.config(text=filein.readline())
    except KeyboardInterrupt:
        pass