Chapter 9 - GUI Programming using Tkinter - Programming Exercises - Page 309: 9.25

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# 9.25 (Traffic lights) Write a program that simulates a traffic light. The program lets the # user select one of three lights: red, yellow, or green. When a radio button is # selected, the light is turned on, and only one light can be on at a time (see # Figure 9.36a–b). No light is on when the program starts. from tkinter import * class MainGUI: def __init__(self): window = Tk() self.canvas = Canvas(window, width=250, height=290, bg='white') self.canvas.create_rectangle(90, 10, 165, 245) self.canvas.create_oval(95, 15, 160, 80, tags="r") self.canvas.create_oval(95, 95, 160, 160, tags="y") self.canvas.create_oval(95, 175, 160, 240, tags="g") self.canvas.pack() frame = Frame(window) frame.pack() var = IntVar() Radiobutton(frame, text="Red", command=self.red, variable=var, value=1).grid(row=1, column=1) Radiobutton(frame, text="yellow", command=self.yellow, variable=var, value=2).grid(row=1, column=2) Radiobutton(frame, text="green", command=self.green, variable=var, value=3).grid(row=1, column=3) window.mainloop() def red(self): self.canvas.delete("all") self.canvas.create_rectangle(90, 10, 165, 245) self.canvas.create_oval(95, 15, 160, 80, tags="r", fill="red") self.canvas.create_oval(95, 95, 160, 160, tags="y") self.canvas.create_oval(95, 175, 160, 240, tags="g") def yellow(self): self.canvas.delete("all") self.canvas.create_rectangle(90, 10, 165, 245) self.canvas.create_oval(95, 15, 160, 80, tags="r") self.canvas.create_oval(95, 95, 160, 160, tags="y", fill="yellow") self.canvas.create_oval(95, 175, 160, 240, tags="g") def green(self): self.canvas.delete("all") self.canvas.create_rectangle(90, 10, 165, 245) self.canvas.create_oval(95, 15, 160, 80, tags="r") self.canvas.create_oval(95, 95, 160, 160, tags="y") self.canvas.create_oval(95, 175, 160, 240, tags="g", fill="green") MainGUI()