StringVar not updating-CodePudding

This question has been popping up a few times here on SO. I notice that most are dead because there is no minimal working example included so I have included that this time. The other thing that happens a lot, seemingly, is multiple Tk instances, so I did my best to keep it to one.

The problem is that I cannot update the label in the InfoPane using a button in the AssetTree. I think that I do not really share the variable but make a copy of it. I'd like to make a pointer of self.shared_data to parent.shared_data but this is Python.

import random
import tkinter as tk
from tkinter import ttk


class AssetTree(tk.Frame):
    def __init__(self, parent):
        super().__init__()
        self.config(background='white')
        self.shared_data = parent.shared_data
        self.button = ttk.Button(self, text="Test", command=self.btn)
        self.button.pack()

    def btn(self):
        print('click')
        print(self.shared_data)
        self.shared_data.set("HELLO")


class InfoPane(tk.Frame):
    def __init__(self, parent):
        super().__init__()

        self.config(height=100, width=100, background='blue')
        self.label = ttk.Label(self, text=parent.shared_data.get())
        self.label.pack()


class MainApplication(tk.Frame):
    def __init__(self, parent, *args, **kwargs):
        tk.Frame.__init__(self, parent, *args, **kwargs)
        self.parent = parent
        self.shared_data = tk.StringVar()

        self.assettree = AssetTree(self)
        self.infopane = InfoPane(self)

        self.assettree.pack(side="left", fill="both", expand=True)
        self.infopane.pack(side="right", fill="both", expand=True)


if __name__ == "__main__":
    root = tk.Tk()
    root.title("Xyrim")
    MainApplication(root).pack(side="top", fill="both", expand=True)
    root.mainloop()

CodePudding user response：

self.label = ttk.Label(self, text=parent.shared_data.get())

This will set the label's text to the text currently in shared_data, but it won't update it when the textvariable changes later.

Try using the textvariable argument instead.

self.label = ttk.Label(self, textvariable=parent.shared_data)

CodePudding user response：

Try this instead

class AssetTree(tk.Frame):
    def __init__(self, parent):
        super().__init__()
        self.config(background='white')
        self.parent = parent  # get parent
        self.button = ttk.Button(self, text="Test", command=self.btn)
        self.button.pack()

    def btn(self):
        print('click')
        self.parent.shared_data.set("HELLO")  # use 'self.parent' here

Same deal here...

class InfoPane(tk.Frame):
    def __init__(self, parent):
        super().__init__()
        self.parent = parent  # get parent
        self.config(height=100, width=100, background='blue')
        # update the label to use 'shared_data' as its textvariable
        # this will update your label's text whenever 'shared_data' changes
        self.label = ttk.Label(self, textvariable=self.parent.shared_data)
        self.label.pack()