queue

myqueue.py

class myqueue:
    def __init__(self):
        self._contents = list()

    def __str__(self):
        return '{}'.format(self._contents[::-1])

    def __iter__(self):
        return iter(self._contents)

    def __len__(self):
        return len(self._contents)

    def enqueue(self, item):
        self._contents.append(item)

    def dequeue(self):
        last = None
        try:
            last = self._contents.pop(0)
        except Exception:
            print('Empty queue!')
        return last

    def front(self):
        return self._contents[0] if len(self) else None

    def back(self):
        return self._contents[-1] if len(self) else None

if __name__ == '__main__':
    q1 = myqueue()
    print(q1)
    print(len(q1))

    [q1.enqueue(x) for x in range(5)]
    print(q1)

    print('front:', q1.front())
    print('back:', q1.back())

    [print('dequeue:', q1.dequeue()) for _ in range(len(q1))]

    x = q1.dequeue()
    print('x:', x)
    print('back:', q1.back())

playlist.py

from myqueue import myqueue

class song:
    def __init__(self, name, artist, duration):
        self.name = name
        self.artist = artist
        self.duration = duration # in seconds

    def __str__(self):
        return '{} -- {} ({})'.format(self.name, self.artist, self.duration)

class playlist:
    def __init__(self):
        self._songs = myqueue()

    def __str__(self):
        songs = []
        [songs.append(str(idx + 1) + '. ' + str(song)) for idx, song in enumerate(self._songs)]
        return '\n'.join(songs)

    def now_playing(self):
        if len(self._songs):
            print('Now playing: {}'.format(self._songs.front()))

    def song_finished(self):
        self._songs.dequeue()

    def add(self, song):
        self._songs.enqueue(song)

if __name__ == '__main__':
    songs = ( ("Singin' in the rain", 'Gene Kelly', 173),
              ('My way', 'Frank Sinatra', 277),
              ("It's the end of the world", 'R.E.M.', 244) )

    p = playlist()

    for (title, artist, duration) in songs:
        s = song(title, artist, duration)
        p.add(s)

    print(p)
    p.now_playing()

    print()
    p.song_finished()
    print(p)
    p.now_playing()