Voice TV Control Voice TV Control
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The technologies are rapidly evolving - only 50 years ago a simple black-and-white TV was a luxury! And now even a cool big color TV with remote control is a common thing. Let's try to improve our TV and add the voice control to it! To begin with, we’ll write the simple prototype in Python. It’ll use the following commands:

first_channel() - turns on the first channel from the list.
last_channel() - turns on the last channel from the list.
turn_channel(N) - turns on the N channel. Pay attention that the channel numbers start from 1, not from 0.
next_channel() - turns on the next channel. If the current channel is the last one, turns on the first channel.
previous_channel() - turns on the previous channel. If the current channel is the first one, turns on the last channel.
current_channel() - returns the name of the current channel.
is_exist(N/'name') - gets 1 argument - the number N or the string 'name' and returns "Yes", if the channel N or 'name' exists in the list, or "No" - in the other case.

The default channel turned on before all commands is №1.
Your task is to create the VoiceCommand class and methods described above.
In this mission you could use the Iterator design pattern.


CHANNELS = ["BBC", "Discovery", "TV1000"]

controller = VoiceCommand(CHANNELS)

controller.first_channel() == "BBC"
controller.last_channel() == "TV1000"
controller.turn_channel(1) == "BBC"
controller.next_channel() == "Discovery"
controller.previous_channel() == "BBC"
controller.current_channel() == "BBC"
controller.is_exist(4) == "No"
controller.is_exist("BBC") == "Yes"

Input: The voice commands.

Output: The channel name or result of the is_exist method.

How it is used: For work with the iterable objects.

Precondition: All commands and channel names are correct.