为什么我按下按键后没有不显示图片呢？

janus123

代码如下

1. 
   
2. import os,sys,math,random,time  
   
3. from glob import glob   
   
4. 
   
5. #from time import sleep
   
6. from Tkinter import *   
   
7. import Image   
   
8. from ImageTk import PhotoImage
   
9. 
   
10. def ran():
    
11.   num = random.randint(1,44)
    
12.   print num
    
13.   try:
    
14.     imgpath = "pic/" + str(num) + ".JPG"
    
15.     print imgpath
    
16.     img = PhotoImage(file=imgpath)
    
17.     canvas.create_image(0,0,image=img,anchor="nw")
    
18.   except IOError:
    
19.     showerror('Photos',"This file isn't image.")
    
20.     pass
    
21. 
    
22. #=======init======#
    
23. top = Tk()
    
24. b1 = Button(top,text='start',command=ran)
    
25. b1.pack(side='left')
    
26. canvas = Canvas(top)
    
27. canvas.config(width=1024,height=768)
    
28. #img = PhotoImage(file="pic/12.jpg")
    
29. canvas.pack(side='top',expand='YES',fill='both')
    
30. #canvas.create_image(0,0,image=img,anchor="nw")
    
31. #imglist = [img for img in os.listdir('./pic')]
    
32. #==================#
    
33. 
    
34. 
    
35. top.mainloop()
    
36. 
    
37. 
    

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