class DeluxeTV(Television):
"""
Just like a standard television, but with additional support for
maintaining and using a set of favorite channels.
"""
def __init__(self):
"""
Creates a new Television instance.
The power is initially off. Upon the first time the TV is turned on,
it will be set to channel 2, and a volume level of 5.
The television maintains a list of favorite channels, initially empty.
"""
Television.__init__(self) # parent constructor
self._favorites = SortedSet()
def addToFavorites(self):
"""
Adds the current channel to the list of favorites, if not already there.
If power is off, there is no effect.
"""
if self._powerOn:
self._favorites.append(self._channel)
def removeFromFavorites(self):
"""
Removes the current channel from the list of favorites, if present.
If power is off, there is no effect.
"""
if self._powerOn and self._channel in self._favorites:
self._favorites.remove(self._channel)
def jumpToFavorite(self):
"""
Jumps to the 'next' favorite channel as per the following rules.
In general, this behavior jumps from the current channel
setting to the next higher channel which is found in the set
of favorites. However if there are no such higher channels,
it jumps to the overall minimal favorite. If there are no
favorites at all, this has no effect on the channel setting.
Returns the resulting channel setting.
If power is off, there is no effect.
"""
if self._powerOn and len(self._favorites)>0:
resultIndex = self._favorites.indexAfter(self._channel)
if resultIndex == len(self._favorites):
result = self._favorites[0] # wrap around
else:
result = self._favorites[resultIndex]
self.setChannel(result)
return result
def __init__(self):
"""
Creates a new Television instance.
The power is initially off. Upon the first time the TV is turned on,
it will be set to channel 2, and a volume level of 5.
The television maintains a list of favorite channels, initially empty.
"""
Television.__init__(self) # parent constructor
self._favorites = SortedSet()