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 Tuesday, November 29.

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 2.

   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")
   

2. 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.