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.