gui_long_distance.py

# resources:
#   + https://www.tutorialspoint.com/python/python_gui_programming.htm
#   + https://www.tutorialspoint.com/python/tk_radiobutton.htm
#   + https://www.tutorialspoint.com/python/tk_entry.htm

from Tkinter import *

window = Tk()

#
# define variables to hold user input values:
#

cents_per_minute = IntVar()
number_of_minutes = StringVar() # needs to be string type, not integer type, because of Entry "textvariable" parameter requirements

#
# define the funtion that will be invoked when radio buttons are selected:
#

def display_total_charges():
    rate = cents_per_minute.get()
    mins = number_of_minutes.get()
    if mins == '': # if the string has not yet been input, it will default to '', which can't be converted to integer (throws: "ValueError: invalid literal for int() with base 10: ''"), so prompt the user to input
        message = "Please enter the length of the call in minutes, then select a rate"
    else:
        mins = int(mins)
        total_cents = rate * mins
        total_dollars = total_cents / 100.00
        message = "Cents Per Minute: " + str(rate) + ". Number of Minutes: " + str(mins) + ". Total Charges (USD): $" + str(total_dollars)

    label.config(text = message)

#
# define GUI elements:
#

minutes_input_label = Label(window, text="Length of Call (in minutes):")
minutes_input = Entry(window, textvariable=number_of_minutes)

daytime_button = Radiobutton(window, text="Daytime (6:00 am through 5:59 pm)", variable=cents_per_minute, value=7, command=display_total_charges)
evening_button = Radiobutton(window, text="Evening (6:00 pm through 11:59 pm)", variable=cents_per_minute, value=12, command=display_total_charges)
offpeak_button = Radiobutton(window, text="Off-Peak (midnight through 5:59 am)", variable=cents_per_minute, value=5,command=display_total_charges)

label = Label(window)

#
# package elements / bind to window:
#

minutes_input_label.pack()
minutes_input.pack()

daytime_button.pack(anchor = W)
evening_button.pack(anchor = W)
offpeak_button.pack(anchor = W)
label.pack()

#
# open main window / run application:
#

window.mainloop()