Untitled

import tkinter
class BMI:
    def __init__(self):
        
        self.mw = tkinter.Tk()
        
        #  cteate an entry
        self.label1= tkinter.Label(self.mw, text='Weight')
        self.entry1 = tkinter.Entry(self.mw, width= 15)
        self.label2 = tkinter.Label(self.mw, text='Height')
        self.entry2 = tkinter.Entry(self.mw, width= 15)
        #  label for calculate button
        self.lab_var = tkinter.StringVar()
        self.lab1 = tkinter.Label(self.mw, textvariable= self.lab_var)      
        
        self.button = tkinter.Button(self.mw, text = 'Calculate BMI', command = self.get_BMI)
        self.lab1.grid(row=2, column=0)
        self.label1.grid(row=0, column=0)
        self.entry1.grid(row=0, column=1)
        self.label2.grid(row=1, column=0)
        self.entry2.grid(row=1, column=1)
        self.button.grid(row=2, column=2)
        
        tkinter.mainloop()  
    def get_BMI(self):
        BMI = float(self.entry1.get())/ (float(self.entry2.get()) * float(self.entry2.get()))
        if BMI < 18.5:
            message = f'Your BMI is {BMI}. You are underweight'
        elif 18.5 < BMI < 24.9:
            message = f'Your BMI is {BMI}. You are healthy'
        elif 25.0 < BMI < 29.9:
            message = f'Your BMI is {BMI}. You are Overweight'
            
        else: 
            message = f'Your BMI is {BMI}. You are obese'
        
        self.lab_var.set(message)
        
gui = BMI()