progressive.py

"""Public domain, yo.
See http://brianna.laugher.id.au/blog/79/the-progressive-speaking-stack-in-python for background.
"""

class Speaker:
    def __init__(self, name):
        self.name = name
        self._hasSpoken = False

    def __eq__(self, other):
        return self.name == other.name

    def __str__(self):
        return 'Speaker<{}>'.format(self.name)

    def speak(self):
        self._hasSpoken = True
        return '{}!'.format(self.name*3)

    def privilege(self):
        """A more accurate implementation is
        left as an exercise to the reader.
        """
        return self._hasSpoken


class ProgressiveStack:
    """I can't help noting that this is actually a queue
    not a stack. ahem.
    In real code I would also implement len, contains, etc.
    """
    def __init__(self, sortMethod):
        """
        @param sortMethod: a function used to sort queue items
        such that the first-sorted item will be selected first
        (so smaller values = selected earlier).
        """
        self._queue = []
        self._sortMethod = sortMethod

    def __str__(self):
        return 'ProgressiveStack<[{}]>'.format(','.join(str(i) for i in self._queue))

    def __iter__(self):
        return self

    def next(self):
        bestChoice = self._queue.pop(0)
        return bestChoice

    def add(self, item):
        self._queue.append(item)
        self._queue.sort(key=self._sortMethod)