Hacking DictMixin to give me access to a list in 2 dimensions

gistfile1.txt

"""
Map stuff

Legend::
    '#' = wall
    '.' = ground
    '+' = door
    ' ' = nothing
"""

from UserDict import DictMixin

class BaseMap(DictMixin):
    """
    Base map class
    """
    def __init__(self, width, height, fill=' '):
        """
        Init the structures for the map, and fill the initial map with fill
        """
        self.width = width
        self.height = height
        # Map is stored as a single list
        self.tiles = [fill]*(width*height)

    def __getitem__(self, key):
        x,y = key
        return self.tiles[y*self.width+x]

    def __setitem__(self, key, value):
        x,y = key
        self.tiles[y*self.width+x] = value

    def keys(self):
        return [(x, y) for x in range(self.width) for y in range(self.height)]

    def generate(self):
        """
        Generate the map
        """
        pass

    def __str__(self):
        rows = []
        for line in range(self.height):
            rows.append(''.join(
                self.tiles[line*self.width:(line+1)*self.width]))
        return '\n'.join(rows)

    def __repr__(self):
        return self.__str__()