I don't understand where the problem is coming from.

Python Help
1

Hello everyone,
I’m having a small problem with my code, and I can’t figure out the cause. I’m trying to reproduce a chess game to learn, and I’m just getting started, but I don’t understand why the image I’m displaying isn’t staying. I’ve tried so many things for several days, but nothing works. I’m desperate…

It would be really great if we could find a solution…

Thanks in advance.

PS: I apologize in advance. I’m French, hence my probably not very good English and my variables in French.

from tkinter import
import tkinter as Tk

fn = Tk.Tk() 
fn.title("échec & Co")
Taille = 80
canvas = Canvas(width=Taille*8,height=Taille*8) #créer un canva de 8 fois la taille des cases en hauteur et en largeur (il y as 8 cases de haut et de large sur un plateau d'échec)
canvas.pack()
echiquier = []

def gen_terrain(echiquier):
    for rangée in range (0,8):
        listeRangée = []
        for colonne in range(0,8):
            if colonne%2 != rangée%2 :
                couleur = 'black'
            else:
                couleur = 'white'
            listeRangée.append(couleur) 
            canvas.create_rectangle(colonne*Taille,rangée*Taille,colonne*Taille+Taille,rangée*Taille+Taille,fill=couleur)
        echiquier.append(listeRangée)
        print(listeRangée)
    print("gen_terrain fin")

def placer_piece(position_cible, piece_a_placer):
    X = (int(list(position_cible)[0]) - 1) * Taille + Taille * 0.5
    Y = (int(list(position_cible)[1]) - 1) * Taille + Taille * 0.5
    Image = Tk.PhotoImage(file="image/Pb.png")
    canvas.create_image(X, Y, image=Image)
    canvas.update()
    print("pion placé")

gen_terrain(echiquier)
placer_piece("11", "Pion")
fn.mainloop()
2

You’re creating a PhotoImage and passing it to create_image.

However, tkinter doesn’t keep a reference to it. (That’s an idiosyncracy of tkinter.)

The only reference to it is the local variable Image.

When placer_piece returns, Image ceases to exist, and there are no references to the image, so it’s garbage-collected.

The solution is to keep a reference to the image yourself, in a global variable in the case of your code.

3

Great! thank you very much! it works!
But to better understand, and not make the same mistake again, what is the garbage collector?

4

The garbage collector disposes of objects that you’re no longer using, freeing up their memory.

For example, you might make a list and use it. When you no longer need it, you don’t have to explicitly tell Python to dispose of it. It’s disposed of automatically.