# -*- coding: utf-8 -*-
import tkinter as tk
root = tk.Tk()
root.title("tk12.py")
root.geometry("300x200")
#####################################
def BMI(event):
    w = float(eWeight.get())
    h = float(eHeight.get())
    bmi = w/h/h
    
    if bmi < 18.5:
        bmitext = '太輕了，要多吃一點'
        lbBMI.config(fg = 'magenta', bg = 'lightgreen')
    elif 18.5<=bmi<23.9:
        bmitext = '標準身材，請好好保持'
        lbBMI.config(fg = 'blue', bg = 'lightpink', font = 'Harrington 12')
    elif 23.9<=bmi<27.9:
        bmitext = '喔喔！得控制一下飲食了\n請加油！'
        lbBMI.config(fg = 'red', bg = 'gold', font = '標楷體 14 italic')
    else:
        bmitext = '肥胖容易引起疾病\n得要多多注意自己的健康囉！'
        lbBMI.config(fg = 'white', bg = 'black', font = 'Times 16 bold')
    lbBMI.config(text = 'Your BMI = {}\n{}'.format(bmi,bmitext))

lbWeight = tk.Label(root, text = '請輸入體重(公斤)'\
                    , font="標楷體")
eWeight = tk.Entry(root, bg = 'lightgreen',\
     bd = 2, font = "標楷體", width = 50)
lbHeight = tk.Label(root, text = '請輸入身高(公尺)'\
                    , font="標楷體")
eHeight = tk.Entry(root, bg = 'lightgreen',\
     bd = 2, font = "標楷體", width = 50)
btBMI = tk.Button(root, text = 'BMI')
lbBMI = tk.Label(root)

lbWeight.pack()
eWeight.pack()
lbHeight.pack()
eHeight.pack()
btBMI.pack()
lbBMI.pack()

btBMI.bind('<1>', BMI)
#####################################
root.mainloop()