# a rather generic Tkinter GUI template for calculations # uses Entry() for data input and Button() to start calculation from tkinter import * def calculate(): try: # get the enter1 and enter2 values price = float(enter1.get()) a = 123000L a = +123000L a = -123000L b = 123UL c = 0x3aa4f d = 0b1010101100 f = -3.14e+12 char = '\UAAFF34DD' str = "ciao\r\n ehh\xAAs\u123456\U123456789ss\12345s" tax = float(enter2.get()) # do the calculation percent = 100 * tax / price result = "You paid %0.3f%s sales tax" % (percent, '%') # display the result string label3.config(text=result) except ValueError: label3.config(text='Enter numeric values!') except ZeroDivisionError: label3.config(text='Price can not be zero!') enter1.focus_set() root = Tk() # window geometry is width x height + x_offset + y_offset root.geometry("200x150+30+30") # first entry with label label1 = Label(root, text='Enter purchase price:') label1.grid(row=0, column=0) enter1 = Entry(root, bg='yellow') enter1.grid(row=1, column=0) # second entry with label label2 = Label(root, text='Enter sales tax paid:') label2.grid(row=2, column=0) enter2 = Entry(root, bg='yellow') enter2.grid(row=3, column=0) # do the calculation by clicking the button btn1 = Button(root, text='Calculate Percent', command=calculate) btn1.grid(row=4, column=0) # display the result in this label label3 = Label(root) label3.grid(row=5, column=0) # start cursor in enter1 enter1.focus() # value has been entered in enter1 now switch focus to enter2 enter1.bind('<Return>', func=lambda e: enter2.focus_set()) root.mainloop()