TkInter: how to wait until callback from after method has completed

Question

When using the Tkinter .after method, the code continues passed without waiting for the callback to complete.

import tkinter as tk
import tkinter.ttk as ttk
import time
from datetime import datetime

global i
i = 0
global j
j = 0

def SomeFunction():
    global i
    for num in range(10):
        i+=1
        x = barVar.get()
        barVar.set(x+5)
        histrun_mainWindow.update()
        time.sleep(2)

def SecondFunction():
    global j
    for num in range(10):
        j+=1
        x = barVar.get()
        barVar.set(x+5)
        histrun_mainWindow.update()
        time.sleep(2)

def Load(run_date):
    histrun_mainWindow.after(50, SomeFunction)
    histrun_mainWindow.after(50, SecondFunction)
    global i, j 
    print 'Number is :', i + j

histrun_mainWindow = tk.Tk()
run_date = datetime.today().date()
barVar = tk.DoubleVar()
barVar.set(0)
bar = ttk.Progressbar(histrun_mainWindow, length=200, style='black.Horizontal.TProgressbar', variable=barVar, mode='determinate')
bar.grid(row=1, column=0)
button= tk.Button(histrun_mainWindow, text='Run for this date ' + str(run_date), command=lambda:Load(run_date))
button.grid(row=0, column=0)
histrun_mainWindow.mainloop()

This example shows what is happening. The .after() calls the Load() function but doesn't wait for Load() to complete, it goes straight on to the next line.

I want i to print as 10 but because the .after() doesn't wait for Load() to finish it's additions, i prints as 0

The progress bar continues to update so I know that Load was called as it continues in the background after i is printed

Answer 1

Question: the progress bar doesn't update - the window freezes until all functions have completed

Use a Thread to prevent main loop from freezing .
Your functions - SomeFunction , SecondFunction - may also in global namespace.
Then you have to pass self.pbar as paramter, eg SomeFunction(pbar): ... f(self.pbar) .

---

Note :
You see a RuntimeError: main thread is not in main loop
if you .destroy() the App() window while the Thread is running !

import tkinter as tk
import threading

class App(tk.Tk):
    def __init__(self):
        super().__init__()
        btn = tk.Button(self, text='Run', 
                              command=lambda :threading.Thread(target=self.Load).start())
        btn.grid(row=0, column=0)
        self.pbar = ttk.Progressbar(self, maximum=2 *(5 * 5), mode='determinate')
        self.pbar.grid(row=1, column=0)

    def SomeFunction(self):
        for num in range(5):
            print('SomeFunction({})'.format(num))
            self.pbar['value'] += 5
            time.sleep(1)
        return num

    def SecondFunction(self):
        for num in range(5):
            print('SecondFunction({})'.format(num))
            self.pbar['value'] += 5
            time.sleep(1)
        return num

    def Load(self):
        number = 0
        for f in [self.SomeFunction, self.SecondFunction]:
            number += f()
        print('Number is :{}'.format(number))

if __name__ == "__main__":
    App().mainloop()

Output :

 SomeFunction(0) SomeFunction(1) SomeFunction(2) SomeFunction(3) SomeFunction(4) SecondFunction(0) SecondFunction(1) SecondFunction(2) SecondFunction(3) SecondFunction(4) Number is :8 

Tested with Python: 3.5 *) Could not test with Python 2.7