[Tutor] properties beginner M Dawson book

[Nicholas Harman]

Hi,
I am teaching myself Python with the book :Python Programming for the Absolute Beginner, 3rd edition by M Dawson.  It is an excellent book and I am enjoying completing the challenges at the end of each chapter.  There are, unfortunately, no answers nor examples of good and bad code.  Honestly I don’t want to “cheat” but I have to teach Python to some young students in September, using this book, and I want all the responses to any doubts they have ready .....
  
Here’s something specific:
chapter 8 challenge 2:  “ Write a program that simulates a television by creating it as an object. The user should be able to enter a channel number and raise or lower the volume.  Make sure that the channel number and volume level stay within valid ranges.”

I have done a little programming in BlueJ Java before but I decided to try the “Python style” as explained in the chapter, using properties rather than variables and getters and setters .....
My main question is:  When using property and setter it seems I must use “__name” or “__volume” (Python’s version of private variables).  Is this true?

Here are parts of my code: - any comments about how bad / good this code is for the level in the book (NOT advanced stuff please) would be greatly appreciated. Thank you

class Television(object):


    #Contstructor
    def __init__(self, name, channel = 1, volume = 5):
        print("A television has been made!")
        #As I am using properties these assignments indirectly call the
        #relevant property setter methods listed below
        self.name = name
        self.channel = channel
        self.volume = volume
        #Note:  "self.__name = name" works but then no call is made to the property setter method


    @property
    def name(self):
        return self.__name

    @name.setter
    def name(self, newName):
        if newName != "":
            self.__name = newName
            print("This TV is now called: ", self.__name)
        else:
            print("Sorry, empty string not allowed as a name.")
            #If the setter was called in the middle of the program run
            #that is it already has an attribute self.__name with a value
            #So leave the namae as it was, unchanged.
            try:
                print("The name stays as: ", self.__name)
                #This will generate an attribute error when called as part of the __init__
                #because self.name has not yet been created nor assigned.
                #So catch this error and give self.__name a "default name"
            except AttributeError:
                self.__name = "Default"
                print("The TV is now called: ", self.__name)


and ............

def main():

    tv_name = input("What do you want to call your television?  ")
    tv = Television(tv_name)
    
    
    choice = None  
    while choice != "0":
        print \
        ("""
        TV Maker
    
        0 - Quit
        1 - Television Details
        2 - Set Channel
        3 - Set Volume
        4 - Chanage the name of the TV
        """)
    
        choice = input("Choice: ")
        print()

        # exit
        if choice == "0":
            print("Good-bye.")

        # Print details of television
        elif choice == "1":
            print("Television details.")
            print(tv)
        
        # Change the channel
        elif choice == "2":
            amount = int(input("Enter 1 to 100 to choose a channel. "))
            tv.channel = amount
         
        # Change the volume
        elif choice == "3":
            amount = int(input("Enter 0 to 10 set the volume. "))
            tv.volume = amount

        elif choice == "4":
            print("Choose a new name for your television but not nothing!")
            tv.name = input("Enter a new name here: ")

        # some unknown choice
        else:
            print("\nSorry, but", choice, "isn't a valid choice.")