如何在同一Tkinter Toplevel（）窗口上显示两个图像

因此，我正在构建一个可以比较两张照片的应用程序。我在屏幕左侧放置了一个列表框，在屏幕右侧放置了两张照片的位置。列表框下面有三个按钮，用于将图片放置在特定标题下（图片1或图片2）。它可以工作，但是我只能在Pic 1和Pic 2上都放一张照片-如果我选择一张照片并将其放在Pic 1下，然后选择另一张照片并将其放在Pic 2下，则第一张照片将消失。

为了更好地了解我的问题，以下是我的应用中的照片浏览功能。

from Tkinter import *
import tkMessageBox
from PIL import ImageTk, Image

def photo_browse ():

    def add_photo (screen, column_num):

        if not "pic" in globals ():
            tkMessageBox.showerror ("Error!", "No picture selected!")
            screen.lift ()
        else:
            screen.image = pic
            can = Label (screen, image = pic)
            can.grid (row = 0, column = column_num)
            Label (screen, text = chosen_photo).grid (row = 1, column = column_num)

    def selection_listbox (evt):

        global chosen_photo
        chosen_photo = str (photo_listbox.get (photo_listbox.curselection ()))
        image_location = "Pics/" + chosen_photo
        global pict
        pict = Image.open (image_location)
        global pic
        pic = ImageTk.PhotoImage (pict)

    import glob

    photo_browse_screen = Toplevel ()
    photo_browse_screen.title ("Photo browse")
    photo_browse_screen.geometry ("1000x600")
    photo_browse_screen.resizable (0, 0)
    photo_listbox = Listbox (photo_browse_screen, width = 50, height = 35)
    photo_listbox.grid (columnspan = 3)
    photo_listbox.bind ('<<ListboxSelect>>', selection_listbox)
    name_list = glob.glob ("Pics/*.jpg")
    name_list = [i [6:] for i in name_list]
    name_list.sort ()
    n = 1
    m = 0
    for i in name_list:
        photo_listbox.insert (n, name_list [m])
        n += 1
        m += 1
    Button (photo_browse_screen, text = "PIC 1", command = lambda: add_photo (photo_browse_screen, 4)).grid (row = 1, column = 0)
    Button (photo_browse_screen, text = "PIC 2", command = lambda: add_photo (photo_browse_screen, 5)).grid (row = 1, column = 1)
    Button (photo_browse_screen, text = "EXIT", command = photo_browse_screen.destroy).grid (row = 1, column = 2)
    can_pic_1 = Label (photo_browse_screen, text = "Pic 1", font= "-weight bold")
    can_pic_1.grid (row = 0, column = 4, padx = (200, 100), sticky = N)
    can_pic_2 = Label (photo_browse_screen, text = "Pic 2", font= "-weight bold")
    can_pic_2.grid (row = 0, column = 5, padx = (100, 150), sticky = N)

root = Tk ()
root.title ("Main menu")
root.geometry ("1000x600")
root.resizable (0, 0)
main_menu = Menu (root)

photos_menu = Menu (main_menu, tearoff = 0)

main_menu.add_cascade (label = "Photos", menu = photos_menu)
photos_menu.add_command (label = "Browse photos", command = photo_browse)

root.config (menu = main_menu)

root.mainloop ()

在上一个功能（添加照片）中，我将照片调整为308x440尺寸，以便它们完美适合此窗口。

在检查完我的代码之后，我几乎肯定global变量会导致此问题，因此，如果有人可以提供替代方法，我将不胜感激。