Simple implementation of Zelda dungeons in Python

dungeons.py

def floor(size=10):
    """Return a list of rooms represented by dictionaries.

    The list is procedurally generated. Each room is represented by a ``dict``
    with ``'x'``, ``'y'``, and ``'exits'`` keys.

    >>> floor(5)[0]
    {'x': 0, 'y': 0, 'exits': {'up': {...}, 'right': {...}}}
    """

    from random import choice

    # Seed the dungeon with a single room.
    rooms = [dict(x=0, y=0, exits={})]

    # Map the possible exits to the X/Y offsets and the corresponding exit
    # in the adjacent room.
    exits = {'up':    (0, -1, 'down'),
             'down':  (0,  1, 'up'),
             'left':  (-1, 0, 'right'),
             'right': (1,  0, 'left')}

    while len(rooms) < size:
        # Select an exit from a room in the floor that has unused exits.
        extant = choice(filter(lambda r: len(r['exits']) < 4, rooms))
        exit = choice([d for d in exits.keys() if not extant['exits'].get(d)])

        # Connect the new room to the existing room and add it to the floor.
        room = dict(x=extant['x'] + exits[exit][0],
                    y=extant['y'] + exits[exit][1],
                    exits={exits[exit][2]: extant})
        extant['exits'][exit] = room
        rooms.append(room)

    return rooms