python - tkinter tic tac toe program -

i experimenting tkinter , thought of implementing simple tic-tac-toe game. here came with

import tkinter tk  class gui(tk.frame):     def __init__(self, master):         super().__init__(master)         self.parent = master         self.parent.title("tic tac toe")         logo = tk.photoimage(file="x.png")         in range(3):             j in range(3):                 w = tk.label(self,image=logo)                 w.grid(row=i, column=j)          self.pack()  if __name__ == '__main__':     root = tk.tk()     logo = tk.photoimage(file="x.png")     f = gui(root)     root.mainloop() 

when execute nothing being displayed. have image in current folder. verify if doing right changed main part to:

if __name__ == '__main__':     root = tk.tk()     logo = tk.photoimage(file="x.png")     f = gui(root)     in range(3):         j in range(3):             w = tk.label(f,image=logo)             w.grid(row=i, column=j)     f.pack()     root.mainloop() 

by commenting respective code in gui class , works. can tell me why so? ve spent hours trying figure out.

keep reference photoimage not garbage collected. saving object instance variable solve issue:

def __init__(self, master):     super().__init__(master)     self.parent = master     self.parent.title("tic tac toe")     self.logo = tk.photoimage(file="x.png")  # <----     in range(3):         j in range(3):             w = tk.label(self, image=self.logo)  # <---             w.grid(row=i, column=j)      self.pack()