[Tkinter] How to delete existing label?

[Oshadha]

You cannot put the delete anywhere because you no longer have a handle to the label. But that's ok, because you really don't want to delete the label. You want to change the label text.

from tkinter import *
 
units = {
    'length'        : ['meter', 'm'],
    'mass'          : ['kilogram', 'kg'],
    'time'          : ['second', 's'],
    'current'       : ['ampere', 'A'],
    'temperature'   : ['kelvin', 'K']}
 
def search(event):
    name = search_box.get()
    unit = units.get(name)
    if unit:
        result_text['text'] = f'Physical quantity :  {name}\nUnit :  {unit[0]}\nSymbol :  {unit[1]}'
    else:
        result_text['text'] = f'Unit "{name}" not found'
    search_box.delete(0, END)
 
main = Tk()
Label(main, text = '1. Unit & Dimensions').pack()
Label(main, text = 'Search').pack()
search_box = Entry(main, width = 34)
search_box.pack()
search_box.bind('<Return>', search)
results = LabelFrame(main, text = 'Results')
results.pack()
result_text = Label(results, width= 40, height=3)
result_text.pack()

mainloop()

What does the f do,
here,

    if unit:
        result_text['text'] = f'Physical quantity :  {name}\nUnit :  {unit[0]}\nSymbol :  {unit[1]}'
    else:
        result_text['text'] = f'Unit "{name}" not found'
    search_box.delete(0, END)