Tkinter window showing up too early

Question

I'm trying to build a binary lamp in Python using Tkinter. The steps are as follows:

    1. Prompt user for input, using the console/shell.
    2. Draw the lamp
    3. Use mainloop to show the image

However, this doesn't always work as I expect it to.

The code:

    from tkinter import *

    HEIGHT = 235
    WIDTH = 385

    tk = Tk()
    canvas = Canvas(tk, width=WIDTH, height=HEIGHT, bg="grey")


    size = 35

    canvas.pack()
    def dec_to_binh(num, lst):
        if num>1:
            dec_to_binh(num // 2, lst)
        lst.append(num%2)
        return lst
    def dec_to_bin(num):
        answ = dec_to_binh(num, [])
        while len(answ) < 4:
            answ.insert(0,0)
        return answ
    class Diode:
        def __init__(self, x, y, label):
            self.shape = canvas.create_oval(x, y, x+size, y+size, width=4,
                                    outline='black', fill='#232323')
            self.label = canvas.create_text(x+int(size/2), y+size+10, text=str(label))
            self.onOff = 0
        def update(self, num):
            if int(num) == 1:
                canvas.itemconfig(self.shape, fill=oncolor)
                onOff = 1
            else:
                canvas.itemconfig(self.shape, fill='black')
                onOff = 0

    class Lamp:
        def __init__(self):
            self.LEDs = [Diode(100, 100, 8), Diode(150, 100, 4), Diode(200, 100, 2), Diode(250, 100, 1)]
    
        def update(self, number):
            n=0
            for i in self.LEDs:
                i.update(dec_to_bin(number)[n])
                n=n+1


    print("What to show as a binary lamp?")

    answer=int(input())
    while answer > 15 or answer < 0:
        print("Invalid input, can only show between range of 0 to 15 inclusive")
        answer=int(input())
    lamp = Lamp()
    lamp.update(answer)

    tk.mainloop()

The bug: When I run this in my IDE (Wing 101), it patiently waits for me to input the number I want to show before drawing the image. However, if I run it straight from the python shell (i.e. I just click on bin_lamp.py) it opens and creates the tk window and shows a blank screen, without waiting for me to tell it what number I want.

After I actually enter the number, it draws what I want it to, but is there any way I can stop the blank tk window with the blank canvas from actually showing up until I'm done entering the input?

Answer 1

You can either put the input before you create the window with tk = Tk(), or you can leave everything as is, but hide the window and show it once it's done. Simply hide the window after it has been created and show it afterwards:

tk = Tk()
tk.withdraw()
# do all your processing
tk.deiconify()