Why the 1st code runs and 2nd doesn't after defining it?

Question

The 1st code completely works fine.

• 1st Code

   from tkinter import *
   from tkinter import ttk
  
  
   win=Tk()  
   add=StringVar()
   sub=StringVar()
   pro=StringVar()
  
   def Find():
       add.set(float(ent00.get())+float(ent01.get()))
       sub.set(float(ent00.get())-float(ent01.get()))
       pro.set(float(ent00.get())*float(ent01.get()))
  
   ent00=Entry(win, width=15)
   ent00.grid(row=4, column=1, padx=10, pady=10, sticky='w')
   ent01=Entry(win, width=15)
   ent01.grid(row=5, column=1, padx=10, pady=10, sticky='w')
  
   lbl8=Label(win, text="Add", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=6, column=0, padx=20, pady=10, sticky='w')
   ent8=Entry(win, textvariable=add, width=15, state='readonly')
   ent8.grid(row=6, column=1, padx=10, pady=10, sticky='w')
  
   lbl15=Label(win, text="Subtract", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=7, column=0, padx=20, pady=10, sticky='w')
   ent15=Entry(win, textvariable=sub, width=15, state='readonly')
   ent15.grid(row=7, column=1, padx=10, pady=10, sticky='w')
  
   lbl9=Label(win, text="Product", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=8, column=0, padx=20, pady=10, sticky='w')
   ent9=Entry(win, textvariable=pro, width=15, state='readonly')
   ent9.grid(row=8, column=1, padx=10, pady=10, sticky='w')
  
   btn = Button(win, text = 'Calculate', command=Find, bd = '5', width=15, height=2)
   btn.grid(row=11, column=1, padx=20, pady=10)
  
   win.geometry("1400x700+250+250")
   win.mainloop()
  

But when I define it i.e. make it a function (As in the code below), it doesn't work. Also it doesn't even show any error. I am not understanding the reason for this issue.

• 2nd Code:

   from tkinter import *
   from tkinter import ttk
  
   win=Tk()  
  
   def code():
       win=Tk()  
       add=StringVar()
       sub=StringVar()
       pro=StringVar()
  
       def Find():
           add.set(float(ent00.get())+float(ent01.get()))
           sub.set(float(ent00.get())-float(ent01.get()))
           pro.set(float(ent00.get())*float(ent01.get()))
  
       ent00=Entry(win, width=15)
       ent00.grid(row=4, column=1, padx=10, pady=10, sticky='w')
       ent01=Entry(win, width=15)
       ent01.grid(row=5, column=1, padx=10, pady=10, sticky='w')
  
       lbl8=Label(win, text="Add", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=6, column=0, padx=20, pady=10, sticky='w')
       ent8=Entry(win, textvariable=add, width=15, state='readonly')
       ent8.grid(row=6, column=1, padx=10, pady=10, sticky='w')
  
       lbl15=Label(win, text="Subtract", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=7, column=0, padx=20, pady=10, sticky='w')
       ent15=Entry(win, textvariable=sub, width=15, state='readonly')
       ent15.grid(row=7, column=1, padx=10, pady=10, sticky='w')
  
       lbl9=Label(win, text="Product", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=8, column=0, padx=20, pady=10, sticky='w')
       ent9=Entry(win, textvariable=pro, width=15, state='readonly')
       ent9.grid(row=8, column=1, padx=10, pady=10, sticky='w')
  
       btn = Button(win, text = 'Calculate', command=Find, bd = '5', width=15, height=2)
       btn.grid(row=11, column=1, padx=20, pady=10)
  
       win.geometry("1400x700+250+250")
       win.mainloop()
  
   btn1 = Button(win, text = 'OPEN CODE', command=code, bd = '5', width=20, height=2)
   btn1.grid(row=11, column=1, padx=20, pady=10)
   win.geometry("1400x700+250+250")
   win.mainloop()
  

Is there any kind of mistake I am doing leading to its non-working? ______________________

Answer 1

You are redefining win and then performing actions on that, which doesn't seem to play nice together. If you want to clear the screen and place new widgets, here's how I would do it:

from tkinter import *
from tkinter import ttk

win=Tk()  

def code():
    btn1.destroy()
    add=StringVar()
    sub=StringVar()
    pro=StringVar()

    def Find():
        add.set(float(ent00.get())+float(ent01.get()))
        sub.set(float(ent00.get())-float(ent01.get()))
        pro.set(float(ent00.get())*float(ent01.get()))

    ent00=Entry(win, width=15)
    ent00.grid(row=4, column=1, padx=10, pady=10, sticky='w')
    ent01=Entry(win, width=15)
    ent01.grid(row=5, column=1, padx=10, pady=10, sticky='w')

    lbl8=Label(win, text="Add", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=6, column=0, padx=20, pady=10, sticky='w')
    ent8=Entry(win, textvariable=add, width=15, state='readonly')
    ent8.grid(row=6, column=1, padx=10, pady=10, sticky='w')

    lbl15=Label(win, text="Subtract", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=7, column=0, padx=20, pady=10, sticky='w')
    ent15=Entry(win, textvariable=sub, width=15, state='readonly')
    ent15.grid(row=7, column=1, padx=10, pady=10, sticky='w')

    lbl9=Label(win, text="Product", bg="crimson", fg="white", font=("times new roman",15,"bold")).grid(row=8, column=0, padx=20, pady=10, sticky='w')
    ent9=Entry(win, textvariable=pro, width=15, state='readonly')
    ent9.grid(row=8, column=1, padx=10, pady=10, sticky='w')

    btn = Button(win, text = 'Calculate', command=Find, bd = '5', width=15, height=2)
    btn.grid(row=11, column=1, padx=20, pady=10)


btn1 = Button(win, text = 'OPEN CODE', command=code, bd = '5', width=20, height=2)
btn1.grid(row=11, column=1, padx=20, pady=10)
win.geometry("1400x700+250+250")
win.mainloop()

I just removed the three lines modifying win in the code function and added btn1.destroy(), which removes the button we want to stop displaying from the window.