Lecture 22 --- Exercises
========================

Solutions to the problems below must be sent to Submitty for
automatic scoring.  A separate file must submitted for each problem.
Solutions must be submitted by 4 pm on Friday, December 1.

#. What is printed out when the following code is run? Assume 
   that the user clicks on the "Launch" button and nothing else.  Put 
   your answer into a text file and submit it as the answer to
   part 1.

   ::

     from tkinter import *

     class MyApp(object):
         def __init__(self, parent):
             print('Initialized!')
             self.parent = parent
             self.main_frame = Frame(parent)
             self.main_frame.pack()
             self.button1 = Button(self.main_frame, text="Launch", command=self.terminate_program)
             self.button1.configure(width=12, padx="4m", pady="4m")
             self.button1.pack()
             self.button2 = Button(self.main_frame, text="C", command=self.c)
             self.button2.configure(width=12, padx="4m", pady="4m")
             self.button2.pack()
             self.rocket = 2

         def d(self):
             self.rocket += 2

         def c(self):
             print("Launching ... counting", end='')
             for i in range(self.rocket):
                 print('...{}'.format(self.rocket), end='')
                 self.rocket -= 1
             print('...Liftoff!', flush=True)        

         def terminate_program(self):
             self.c()
             print('Terminated')
             self.parent.destroy()

     if __name__ == "__main__":
         root = Tk()
         print("Countdown ready")
         myapp = MyApp(root)
         myapp.d()
         root.mainloop()
         myapp.d()
         print(myapp.rocket)
         myapp.c()
         print("Done")

#. Revisiting the same code, what is printed if the code is run a second time
   and the user clicks the "C" button and 
   nothing else? Put your answer into a text file and submit it as the answer to
   part 2.