为什么 time.sleep 甚至在 window (tkinter) 打开之前就可以工作？

Question

Why does the time.sleep() work before the window of tkinter opens?

Code:

import tkinter
import time
window = tkinter.Tk()
window.geometry("500x500")
window.title("Holst")


holst = tkinter.Canvas(window, width = 450, height = 450, bg = "white")
holst.place(x = 25, y = 25)

x = 30
y = 50
d = 30

circle = holst.create_oval(x, y, x+d, y+d, fill = "red")
time.sleep(2)
holst.move(circle, 50, 40)

Answer 1

You asked that why is time.sleep() is called before the windows loads because you hopefully called the window.mainloop() at the last of the code which loads the window and keep maintain the tkinter window

The time.sleep() function code executes before the window.mainloop() function so it was stop the execution and sleeps before the window could load

A nice approach will be to call the time.sleep() in a if statement.

Answer 2

The Tk instance requires you to run it's mainloop function in order to take control of the main process thread.

Your code is calling time.sleep() on the main process thread, which blocks the GUI from doing anything. If you want to be able to do things with the GUI while waiting (such as drawing the window, moving it around, or drawing other things to it) then you would need to extend Tk to have the UI handle the callback using self.after()

Here's a simple example of how you would extend the Tk class to achieve what you want.

import tkinter

class TkInstance(tkinter.Tk):
    def __init__(self):
        tkinter.Tk.__init__(self)

        #Set up the UI here
        self.canvas = tkinter.Canvas(self, width = 450, height = 450, bg = "white")
        self.canvas.place(x = 25, y = 25) #Draw the canvas widget

        #Tell the UI to call the MoveCircle function after 2 seconds
        self.after(2000, self.MoveCircle) #in ms

    def MoveCircle(self):
        x = 30
        y = 50
        d = 30
        circle = self.canvas.create_oval(x, y, x+d, y+d, fill = "red")
        self.canvas.move(circle, 50, 40) #Draw the circle

#Main entrance point
if __name__ == "__main__": #good practice with tkinter to check this
    instance = TkInstance()
    instance.mainloop()