#!/usr/bin/python3

from tkinter import *
from tkinter import ttk
# define calculate function
def calculate(*args):
    try:
        value=float(feet.get())
        meters.set(int(0.3048 * value * 10000.0 + 0.5)/1000.0)
    except ValueError:
        pass
# Set up Main Application Window
root=Tk()
root.title("Feet to Meters")

# Create Content Frame
mainframe=ttk.Frame(root, padding="3 3 12 12")
# Put grid in Content Frame
mainframe.grid(column=0, row=0, sticky=(N, W, E, S))
root.columnconfigure(0, weight=1)
root.rowconfigure(0, weight=1)
# Create entry widget
feet=StringVar()
feet_entry=ttk.Entry(mainframe, width=7, textvariable=feet)
feet_entry.grid(column=2, row=1, sticky=(W, E))
# Create remaining widgets
meters=StringVar()
ttk.Label(mainframe, textvariable=meters).grid(column=2, row=2,
sticky=(W,E))

ttk.Button(mainframe, text='Calculate', command=calculate).grid(column =3,
row=3, sticky=W)

ttk.Label(mainframe, text="feet").grid(column=3, row=1, sticky=W)
ttk.Label(mainframe, text="is equivalent to").grid(column=1, row=2, sticky=E)
ttk.Label(mainframe, text="meters").grid(column=3, row=2, sticky=W)
# finishing touches
for child in mainframe.winfo_children():
    child.grid_configure(padx=5, pady=5)

feet_entry.focus()
root.bind("<Return>", calculate)
# Tkinter event loop
root.mainloop()