What is the Standard way to Achieve this grid in Tkinter?

I'm trying to create:

UI Im trying to create

I'm Trying to Create this grid layout (ignoring Entry box right now) but I'm Having issue in stretching the 5th row having 5 columns equally. So far, I have achieved this.

so far my output

Code I have coded so far is given below but do let me know the standard way to achieve this grid.

import tkinter as tk

root = tk.Tk()

frame = tk.Frame(root)
frame.pack(expand=True, fill='both')

num = 1
for i in range(0, 3):
    for j in range(0, 3):
        tk.Button(frame, text=num).grid(row=i, column=j, sticky='nsew')
        num += 1
        frame.columnconfigure(i, weight=1)
        frame.rowconfigure(i, weight=1)

tk.Button(frame, text='-').grid(row=4, column=0, sticky='nsew')
tk.Button(frame, text=0).grid(row=4, column=1, sticky='nsew')
tk.Button(frame, text='.').grid(row=4, column=2, sticky='nsew')
frame.rowconfigure(4, weight=1)

frame2 = tk.Frame(frame)
frame2.grid(row=5, columnspan=3)

frame2.rowconfigure(0, weight=1)
frame2.rowconfigure(1, weight=1)
frame2.rowconfigure(2, weight=1)
frame2.rowconfigure(3, weight=1)
frame2.rowconfigure(4, weight=1)

tk.Button(frame2, text='+').grid(row=0, column=0, sticky='nsew')
tk.Button(frame2, text='-').grid(row=0, column=1, sticky='nsew')
tk.Button(frame2, text='*').grid(row=0, column=2, sticky='nsew')
tk.Button(frame2, text='/').grid(row=0, column=3, sticky='nsew')
tk.Button(frame2, text='=').grid(row=0, column=4, sticky='nsew')


root.mainloop()

Solution

Followed by @Thingambobs. frame2.grid(row=5, columnspan=3, sticky='we')

On line 12, add width=5 for Button widget to suit your need.
If you like to add an Entry widget. Just add on line 17 and 18. See snippet.
On line 28, then add button for "CLR" tk.Button(frame, text='CLR', width=5).grid(row=6,column=0,columnspan=5, sticky='we')
These five Button widgets, change sticky to sticky='we'

Snippet:

import tkinter as tk

root = tk.Tk()
#root.grid_propagate()

frame = tk.Frame(root)
frame.grid(row=0, column=0, sticky='nsew')

num = 1
for i in range(0, 3):
    for j in range(0, 3):
        tk.Button(frame, text=num, width=5).grid(row=i+1, column=j, sticky='nsew')
        num += 1
        frame.columnconfigure(i, weight=1)
        frame.rowconfigure(i, weight=5)

entry = tk.Entry(frame, width=25)
entry.grid(row=0, column=0, columnspan=3, sticky='we')

tk.Button(frame, text='-').grid(row=4, column=0, sticky='nsew')
tk.Button(frame, text=0).grid(row=4, column=1, sticky='nsew')
tk.Button(frame, text='.').grid(row=4, column=2, sticky='nsew')
frame.rowconfigure(4, weight=1)

frame2 = tk.Frame(frame)
frame2.grid(row=5, columnspan=3, sticky='we')

tk.Button(frame, text='CLR').grid(row=6, column=0,columnspan=5, sticky='we') 

tk.Button(frame2, text='+', width=5).grid(row=0, column=0, sticky='we')
tk.Button(frame2, text='-', width=5).grid(row=0, column=1, sticky='we')
tk.Button(frame2, text='*', width=5).grid(row=0, column=2, sticky='we')
tk.Button(frame2, text='/', width=5).grid(row=0, column=3, sticky='we')
tk.Button(frame2, text='=', width=5).grid(row=0, column=4, sticky='we')

root.mainloop()

Screenshot: