Lecture 22 — Exercises

Solutions to the problems below must be sent to Submitty for automatic scoring. A separate file must submitted for each problem.

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")
   

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.