The error _tkinter.TclError: bad window path name ".!application" happens because your clear() method is destroying the parent widget itself (your Application instance, self) along with its children. Here's the breakdown:

When you loop through root.winfo_children(), if your self (the app instance) is a child of root (like a Frame inside the main window), then self gets destroyed too. After that, trying to create a new Label with self as the parent fails because self is no longer a valid Tkinter widget.

Fix 1: Clear Only the Children of Your App Instance #

Instead of targeting root, loop through the children of self (your app's widget container). This way, you only destroy the widgets inside self, not self itself:

def clear(self):
    # Destroy all widgets inside self, not root
    for child in self.winfo_children():
        child.destroy()

Fix 2: Use a Dedicated Container Frame (Cleaner Approach) #

For better organization, create a separate frame inside your app to hold all dynamic widgets. This lets you clear only that frame's children without touching other parts of your UI (like menus or toolbars):

import tkinter as tk
import tkinter.font as tkFont

class Application(tk.Frame):
    def __init__(self, master=None):
        super().__init__(master)
        self.master = master
        self.pack(fill="both", expand=True)
        
        # Create a dedicated container for dynamic widgets
        self.dynamic_container = tk.Frame(self)
        self.dynamic_container.pack(fill="both", expand=True)
        
        # Add initial widgets
        self.add_initial_widgets()

    def clear(self):
        # Only destroy widgets inside the dynamic container
        for child in self.dynamic_container.winfo_children():
            child.destroy()

    def add_initial_widgets(self):
        tk.Label(self.dynamic_container, text="Initial Widget").pack(pady=20)

    def add_test_widget(self):
        self.clear()
        # Create new widget inside the valid container
        tk.Label(
            self.dynamic_container, 
            text="test", 
            font=tkFont.Font(family="Arial", size=25)
        ).place(x=0, y=0)

# Run the app
root = tk.Tk()
app = Application(master=root)
app.add_test_widget() # Call this to test clearing and adding new widget
app.mainloop()

Why This Works #

• In Fix 1, we're only removing widgets that are direct children of self, leaving self intact to act as a parent for new widgets.
• In Fix 2, the dynamic_container frame acts as a safe, isolated space for widgets you want to clear and rebuild. Since the container itself never gets destroyed, you can always add new widgets to it without errors.

Quick Note on place() #

When using place(), make sure your container frame has a visible size (either via pack(fill="both", expand=True) or setting explicit width/height values). Otherwise, your new label might be created but not visible.

内容的提问来源于stack exchange，提问作者Nowedit