pathmap.py

class PathMap(object):
    sep = u'.'

    def __init__(self):
        self._store = {}

    def __setitem__(self, key, value):
        segments = key.rstrip(self.sep).split(self.sep)
        next_ = self._store
        for segment in segments:
            if segment not in next_:
                next_[segment] = {}
            next_ = next_[segment]
        next_['__value__'] = value

    def __getitem__(self, key):
        notfound_sentinel = object()
        value = notfound_sentinel
        segments = key.rstrip(self.sep).split(self.sep)
        next_ = self._store
        for segment in segments:
            if '__value__' in next_:
                value = next_['__value__']
            if segment not in next_:
                break
            next_ = next_[segment]
        if value is notfound_sentinel:
            raise KeyError
        else:
            return value

def test_create():
    pm = PathMap()
    pm['a.b.c.'] = 'alphabet'
    pm['this.is.one.'] = ()
    pm['this.is.'] = []
    return pm

def test_first():
    pm = test_create()
    assert pm['a.b.c.d.e'] == 'alphabet'

def test_2():
    pm = test_create()
    assert pm['this.is.one.tuple'] == ()
def test_3():
    pm = test_create()
    assert pm['this.is.a.list'] == []
def test_4():
    pm = test_create()
    try:
        pm['a.b']
    except KeyError:
        pass
    else:
        assert False, "Should have raised a key error"