Gym-MiniGrid/gym_minigrid/envs/blockedunlockpickup.py

from gym_minigrid.minigrid import Ball
from gym_minigrid.roomgrid import RoomGrid


class BlockedUnlockPickupEnv(RoomGrid):
    """
    Unlock a door blocked by a ball, then pick up a box
    in another room
    """

    def __init__(self, **kwargs):
        room_size = 6
        super().__init__(
            num_rows=1,
            num_cols=2,
            room_size=room_size,
            max_steps=16 * room_size**2,
            **kwargs,
        )

    def _gen_grid(self, width, height):
        super()._gen_grid(width, height)

        # Add a box to the room on the right
        obj, _ = self.add_object(1, 0, kind="box")
        # Make sure the two rooms are directly connected by a locked door
        door, pos = self.add_door(0, 0, 0, locked=True)
        # Block the door with a ball
        color = self._rand_color()
        self.grid.set(pos[0] - 1, pos[1], Ball(color))
        # Add a key to unlock the door
        self.add_object(0, 0, "key", door.color)

        self.place_agent(0, 0)

        self.obj = obj
        self.mission = f"pick up the {obj.color} {obj.type}"

    def step(self, action):
        obs, reward, done, info = super().step(action)

        if action == self.actions.pickup:
            if self.carrying and self.carrying == self.obj:
                reward = self._reward()
                done = True

        return obs, reward, done, info