On 12/23/2011 04:21 PM, myles broomes wrote:
Im trying to create a 'Television simulation' program. Heres the code ive
written for it:
#television simulation
#a program that simulates a television
#the user can turn the television on or off, change the volume or change the
channel
#create the television class
class Television(object):
"""A virtual television simulation"""
def __init__(self):
print("The television is off.")
def power_button(self, power = "off"):
if power == "off":
power = "on"
The above line does nothing useful, as the value is thrown out when the
method returns. Same is true in several other places below.
print("The power is now on.")
else:
power = "off"
print("The power is now off.")
def volume_button(self, volume = 0):
up_or_down = input("Do you want to increase or decrease the volume?
(up/down): ")
if up_or_down == "up":
amount = int(input("By how much? (Enter a number): "))
volume += amount
if volume> 10:
volume = 10
print("The volume is now",volume)
elif up_or_down == "down":
amount = int(input("By how much? (Enter a number): "))
volume += amount
if volume< 0:
volume = 0
print("The volume is now",volume)
else:
print("That is not a valid choice.")
def channel_button(self, channel = 1):
new_channel = int(input("What channel do you want to watch? (Enter
a number between 1 and 10.): "))
if new_channel< 1 or new_channel> 10:
print("That is not a valid channel!")
else:
channel = new_channel
print("The channel is now",channel)
#create the main part of the program, the television simulation
def main():
tv = Television()
choice = None
while choice != "0":
print \
("""
Television simulation
0 - Quit
1 - Turn the television on or off
2 - Change the volume
3 - Change the channel
""")
choice = input("Choice: ")
print()
#exit
if choice == "0":
print("Good-bye.")
#turn the television on or off
elif choice == "1":
tv.power_button()
#increase or decrease the volume
elif choice == "2":
tv.volume_button()
#change the channel
elif choice == "3":
tv.channel_button()
else:
print("\nInvalid choice!")
main()
("\n\nPress the enter key to exit.")
It works fine but the problem im having is that when volume, channel or power
are changed inside of their methods, their values dont change in the program if
that makes sense. So i was just wondering if there was a way around this.
Normally when such values are changed in the method, you want a
corresponding attribute of the instance to 'remember' the value. In
your particular program you have one instance, called tv. Each time you
call a method on that instance, such as tv.power_button(), you are
implicitly passing that instance to the method, as the value 'self'.
That's what you're not writing to correctly.
Inside a method, you usually refer to such instance attributes as
self.attribname. So let's try just one of them, the power button.
def power_button(self):
if self.power == "off":
self.power = "on"
else:
self.power = 'off'
print "Power is now ", self.power
Notice I got rid of the unused parameter, since it was never referenced.
One other thing we must do here: In the __init__() method, you need to
initialize the state of the Television instance. You can't just print a
statement saying it's initialized, you have to create each of the
attributes comprising its initial state. In our case, we'd add a line
self.power = "off"
I'll leave the other two attributes to you. There are other things I
could critique, but I want to give you the minimum push to make
something that could run.
--
DaveA
_______________________________________________
Tutor maillist - Tutor@python.org
To unsubscribe or change subscription options:
http://mail.python.org/mailman/listinfo/tutor
