Gym-MiniGrid/gym_minigrid/envs/doorkey.py

from gym_minigrid.minigrid import Door, Goal, Grid, Key, MiniGridEnv, MissionSpace


class DoorKeyEnv(MiniGridEnv):
    """
    Environment with a door and key, sparse reward
    """

    def __init__(self, size=8, **kwargs):
        if "max_steps" not in kwargs:
            kwargs["max_steps"] = 10 * size * size
        mission_space = MissionSpace(
            mission_func=lambda: "use the key to open the door and then get to the goal"
        )
        super().__init__(mission_space=mission_space, grid_size=size, **kwargs)

    def _gen_grid(self, width, height):
        # Create an empty grid
        self.grid = Grid(width, height)

        # Generate the surrounding walls
        self.grid.wall_rect(0, 0, width, height)

        # Place a goal in the bottom-right corner
        self.put_obj(Goal(), width - 2, height - 2)

        # Create a vertical splitting wall
        splitIdx = self._rand_int(2, width - 2)
        self.grid.vert_wall(splitIdx, 0)

        # Place the agent at a random position and orientation
        # on the left side of the splitting wall
        self.place_agent(size=(splitIdx, height))

        # Place a door in the wall
        doorIdx = self._rand_int(1, width - 2)
        self.put_obj(Door("yellow", is_locked=True), splitIdx, doorIdx)

        # Place a yellow key on the left side
        self.place_obj(obj=Key("yellow"), top=(0, 0), size=(splitIdx, height))

        self.mission = "use the key to open the door and then get to the goal"