Limited-length sorted list.

history.py

import bisect
import operator
import unittest

class history:
    """Limited-length sorted list."""
    def __init__(self, maxlen):
        self._maxlen = maxlen
        self._list = []
    def __repr__(self):
        return 'upmonitor.database.history(%r)' % self._heap
    def __len__(self):
        return len(self._list)
    # We do not implement __(get|del)item__ because it would not make sense
    def __setitem__(self, timestamp, value):
        self._list.insert(bisect.bisect_left(self._list, (timestamp, 0)),
                (timestamp, value))
        while len(self._list) > self._maxlen:
            self._list.pop(0)
    def __iter__(self):
        return map(operator.itemgetter(1), self._list)

    def items(self):
        return self.__iter__()

    def reverseitems(self):
        return map(operator.itemgetter(1), reversed(self._list))

class TestHistory(unittest.TestCase):
    def testRing(self):
        history = history(maxlen=5)
        for x in range(1, 10):
            history[x*10 + 50] = str(x)
            self.assertEqual(len(history), min(5, x), history)
            self.assertEqual(len(list(history)), min(5, x), list(history))

    def testOrder(self):
        list_ = [(5, 'baz'), (3, 'bar'), (9, 'qux'), (1, 'foo'), (10, 'quux')]
        history = history()
        for (key, value) in list_:
            history[key] = value
        self.assertEqual(list(history), 'foo bar baz qux quux'.split(' '))
        self.assertEqual(list(history.items()),
                'foo bar baz qux quux'.split(' '))
        self.assertEqual(list(history.reverseitems()),
                'quux qux baz bar foo'.split(' '))