python tkinter-按下按钮时覆盖标签

Question

 def button_pressed(item_name, item_price):
    global lbl
    for v1, v2 in zip(item_name, item_price):
        item_values = '{} {}'.format(v1, v2)
        sv = StringVar()
        lbl = Label(shop_window, height="2", textvariable=sv, anchor = NW).grid(columnspan = 4)
        sv.set(item_values)

# Create initial shopping cart window

shop_window = Tk()
shop_window.title('Welcome to the Outlet')
shop_window.geometry("1200x900")
shop_window.resizable(0, 0)


introduction_text = Label(shop_window, text = 'Welcome to the Shopping Outlet', font = ('Arial', 30))

electronics_button = Button(shop_window, text = 'Buy Electronics', font = ('Arial', 18), command = lambda:button_pressed(electronics_name, electronics_price))
books_button = Button(shop_window, text = 'Buy Books', font = ('Arial', 18), command = lambda:button_pressed(books_name, books_price))
kitchen_button = Button(shop_window, text = 'Buy Kitchen', font = ('Arial', 18), command = lambda:button_pressed(kitchen_name, kitchen_price))
monitors_button = Button(shop_window, text = 'Buy Kitchen', font = ('Arial', 18), command = lambda:button_pressed(monitors_name, monitors_price))

introduction_text.grid(row = 0, column = 0, columnspan = 4, sticky = N )

electronics_button.grid(row = 2, column = 0)
books_button.grid(row = 2, column = 1)
kitchen_button.grid(row = 2, column =2)
monitors_button.grid(row = 2, column = 3)

I've created this tk window to display a shopping list of 10 items per category. Each category has two list, item_name/item_price (they have been scraped off amazon.)

When I run the program I can press the button and the list will display properly but if I press it again it adds new labels to the end of the previously made labels. My questions would be how do I make the program overwrite previous labels for example. Press "Buy Electronics" creates my labels as required, but pressing "Buy Books" after adds more labels. I want to over write the "Buy Electronics" labels. I figured it would be some kind of global lbl but unsure.

Answer 1

see the on the example with function have created, to do that you need to overwrite before positioning the current one there by using lbl["text"] = sv

def button_pressed(item_name, item_price):
    global lbl
    for v1, v2 in zip(item_name, item_price):
        item_values = '{} {}'.format(v1, v2)
       # sv = StringVar()
        lbl["text"] = sv
        sv.set(item_values)

Then create you Label inside root and mainloop

shop_window = Tk()

sv = StringVar()
lbl = Label(shop_window, height="2", textvariable=sv, anchor = NW)
lbl.grid(columnspan = 4)


shop_window = Tk()

Answer 2

You could create a frame for the labels

f = Frame(shop_window)
f.grid(row=3, column=0, columnspan=4)

Then in the callback function destroy all children of the frame and create new ones

def button_pressed(item_name, item_price):
    for widget in f.winfo_children():
        widget.destroy()
    for v1, v2 in zip(item_name, item_price):
        item_values = '{} {}'.format(v1, v2)
        Label(f, height="2", text=item_values).pack()