使用 tkinter 访问函数外的变量

Question

我正在构建一个简单的应用程序，它需要读取两个单独的文件，我有两个功能。 当按下 tk 按钮时，这些函数只会打开一个文件浏览器。

现在，我只想在终端中打印文件名，最终目标是使用文件名更新 tk 标签并在另一个函数中使用。

我在这两个函数中都将每个文件名声明为全局变量，但是如果不调用这些函数就无法访问它们。 如果我调用这些函数，文件资源管理器窗口将在用户不按下按钮的情况下打开。

所以我想我的问题是，有没有办法在不调用函数的情况下访问全局变量？ 当然使用按钮调用应该使全局变量可用的函数吗？

from tkinter import *
from tkinter import filedialog
import os 
# Function for opening the
# file explorer windows

def browseFiles_csv():
    global filename_csv
    filename_csv = filedialog.askopenfilename(initialdir = "/",
                                          title = "Select a File",
                                          filetypes = (("Text files",
                                                        "*.txt*"),
                                                       ("all files",
                                                        "*.*")))
          
    # Change label contents
    csv_label.configure(text="File Opened: "+ os.path.basename(filename_csv))
    return filename_csv

def browseFiles_cfg():
    global filename_cfg
    filename_cfg = filedialog.askopenfilename(initialdir = "/",
                                          title = "Select a File",
                                          filetypes = (("Text files",
                                                        "*.txt*"),
                                                       ("all files",
                                                        "*.*")))
     
    # Change label contents
    cfg_label.configure(text="File Opened: "+ os.path.basename(filename_cfg))
    return filename_cfg 
                                                                                                
# Create the root window
window = Tk()
  
# Set window title
window.title('File Updater')
  
# Set window size
window.geometry("500x250")
  
#Set window background color
window.config(background = "white")
  
# Create a File Explorer label
csv_label = Label(window,
                            text = "Please select a  *.csv file",
                            width = 100, height = 4,
                            fg = "blue")

cfg_label = Label(window,
                            text = "Please select a *.cfg file",
                            width = 100, height = 4,
                            fg = "blue")
  
      
csv_button = Button(window,
                        text = "Select csv",
                        command = browseFiles_csv)

cfg_button = Button(window,
                        text = "Select cgf",
                        command = browseFiles_cfg)
  
button_exit = Button(window,
                     text = "Exit",
                     command = exit)
  
# Place controls
csv_label.grid(column = 1, row = 1)
csv_button.grid(column = 1, row = 2)
cfg_label.grid(column = 1, row = 3)
cfg_button.grid(column = 1, row = 4)
  
button_exit.grid(column = 1,row = 5)

#Using this code I get the file explorer opening before I use the select buttons
#fn_csv = browseFiles_csv()
#fn_cfg = browseFiles_cfg()

# Using this code I get errors with filename_xxx not defined though they are global variables
fn_csv = filename_csv
fn_cfg = filename_cfg

print(fn_csv)
print(fn_cfg)
  
# Let the window wait for any events
window.mainloop()