tkinter grid layout

#!/usr/bin/env python3
import tkinter
root = tkinter.Tk()
a = [[1, 2, 3], [5, 6, 7]]
for i in range(len(a)):
    for j in range(len(a[i])):
        tkinter.Label(
            root, text=str(a[i][j]), fg='white', bg='red', padx=20,
            pady=20).grid(
                column=i, row=j, padx=3, pady=3)
root.mainloop()