Python Tkinter：在画布上单击时获取鼠标坐标作为全局变量

Question

I 've started experiencing Python very recently, moving from Matlab. My code uploads an image on canvas with tkinter. On mouse click on canvas image, I could get the mouse-click coordinates and display them in the console from the respective function (.bind). My problem is that I want to use the mouse-click coordinates as global variables to my code (Cx and Cy in the example below), ie outside .bind events and functions. I understand that tkinter doesn't pause the program to wait for a mouse click event, so, there, I guess, is the issue. I 've noticed that there 've been several similar questions/answers in your site in the past, but still I can't resolve my problem. Should I use other widget, if tkinter cannot support this? Your help and opinion is deeply appreciated. I apology if my question has been already addressed in your site; though I could not find the solution. Here is an example of my code:

import tkinter as tk 
import pandas as pd
import os
import sys

from tkinter.filedialog import askopenfilename
from PIL import Image, ImageTk

print("\033[H\033[J") # to clear the Spyder console
os.system('cls') #on Windows System to clear screen

root = tk.Tk()
w = tk.Canvas(root, width=1000, height=1000)
w.pack()
File = askopenfilename(parent=root, initialdir="./",title='Select an image')
original = Image.open(File)
img = ImageTk.PhotoImage(original)
w.create_image(0, 0, image=img, anchor="nw")

def getcoord(event):
    global Cx, Cy
    Cx = event.x
    Cy = event.y
    print('X = ', Cx, '   Y=  ', Cy)

def quit(event):                           
    sys.exit() 

w.bind('<Button-1>', getcoord)
w.bind('<Double-1>', quit)

root.mainloop()

Answer 1

It is not entirely clear what problem holds you up as your variables Cx and Cy are already available globally. To demonstrate it, here is a minimum example that prionts clicks coords in the console, and every 5 clicks calls another function that prints the coords without receiving a canvas event.

import tkinter as tk


def getcoord(event):
    global Cx, Cy
    Cx, Cy = event.x, event.y
    print('X = ', Cx, '   Y=  ', Cy)
    num_clicks.set(num_clicks.get() + 1)


def five_clicks(*args):
    if not num_clicks.get() % 5:
        print(f'after %5 clicks: {Cx=}, {Cy=}')


if __name__ == '__main__':

    Cx, Cy = 0, 0

    root = tk.Tk()
    num_clicks = tk.IntVar(0)
    num_clicks.set(0)
    num_clicks.trace_add('write', five_clicks)

    w = tk.Canvas(root, width=1000, height=1000)
    w.pack()

    w.bind('<Button-1>', getcoord)

    root.mainloop()