Updating tkinter GUI to show image

Question

I am trying to create a GUI that shows your picture after you upload it. I wrote this code for it. But for some reason, it does not show the image. How can I update the root.mainloop() to show the image?

displaynumber = 0

root = tk.Tk()

f1 = ''
v = tk.IntVar()
def ShowChoice():
    print(v.get())
tk.Label(root, text="""Choose method:""", justify = tk.LEFT, padx = 20).pack()

#uploading file
def selecting():
    global displaynumber
    root.filename =  filedialog.askopenfilename(initialdir = "/",title = "Select file",filetypes = (("jpeg files","*.jpg"),("all files","*.*")))
    f1 = root.filename
    displaynumber = 2
    print (root.filename)

# radio button
tk.Radiobutton(root, text="Select Image from Directory", padx = 20, variable=v, command=selecting, value=1).pack(anchor=tk.W)

# function for displaying image    
if displaynumber > 0:
    global img
    img = ImageTk.PhotoImage(Image.open(f1))
    panel = tk.Label(root, image=img)
    panel.pack(side="bottom", fill="both")
    root.update()   
elif displaynumber ==0:
    pass    

# root mainloop and geometry
root.geometry("1000x500")
root.mainloop()

Answer 1

The problem is that your if statement is not checked in mainloop . mainloop only updates the Tk instances that you added to root ; thus, the code never re-enters your if statement. You could replace mainloop with your own loop that would contain the update_idletasks and update methods. Here is a StackOverflow answer that did a good job explaining tk.mainloop .

You also made an error when using Image.open() . This method takes a file and not a string, so you would need to open that file using the open method before you use it:

with open(f1) as img_file:
    img = ImageTk.PhotoImage(Image.open(f1))

Thus your code should look something like that:

displaynumber = 0

root = tk.Tk()

f1 = ''
v = tk.IntVar()
def ShowChoice():
    print(v.get())

def selecting():
    global displaynumber
    global f1
    root.filename =  filedialog.askopenfilename(initialdir = "/",title = "Select file",filetypes = (("jpeg files","*.jpg"),("all files","*.*")))
    f1 = root.filename
    displaynumber = 2


tk.Label(root, text="""Choose method:""", justify = tk.LEFT, padx = 20).pack()

tk.Radiobutton(root, text="Select Image from Directory", padx = 20,  variable=v, command=selecting, value=1).pack(anchor=tk.W)

root.geometry("1000x500")

# Your new loop
while True:
    if displaynumber > 0:
        global fl
        with open(f1) as img_file:
            img = ImageTk.PhotoImage(Image.open(f1))
        panel = tk.Label(root, image=img)
        panel.pack(side="bottom", fill="both")
        displaynumber = 0
    elif displaynumber ==0:
        pass
    root.update_idletasks()
    root.update()