`obs` is not a dictionary but only has str `'proprioceptive'`.

[psh9002]

I got an error at class UnimalHeightObs(gym.ObservationWrapper), def observation(self, obs): from hfield.py

  File "/home/bak/Projects/metamorph/metamorph/envs/wrappers/hfield.py", line 211, in observation
    obs["torso_height"] = round(z_pos - 1, 3)
TypeError: 'str' object does not support item assignment

The def observation(self, obs): is called from class UnimalEnv(gym.Env): in unimal.py. Though the obs is a dictionary and has 'proprioceptive', 'edges' keys at the end of def reset(self):, obs is just a str 'proprioceptive' at def observation(self, obs): class UnimalHeightObs(gym.ObservationWrapper).

From the viewpoint of the train loop, the error occurs when the code creates (or initializes) the world environment. At ppo.py, obs cannot create at def train(self):.

To solve above issue, I added self.obs_temp = obs at def reset(self): at def reset(self): class UnimalEnv(gym.Env): and obs = self.obs_temp at class UnimalHeightObs(gym.ObservationWrapper), def observation(self, obs):to preserve obs information.

• unimal.py

class UnimalEnv(gym.Env):
    """Superclass for all Unimal tasks."""

...........
...........
    ###########################################################################
    # Reset sim
    ###########################################################################
    def reset(self):
        if self.sim is None or cfg.ENV.NEW_SIM_ON_RESET:
            self.sim = self._get_sim()
        else:
            self.sim.reset()

        self.step_count = 0

        if self.viewer is not None:
            self.viewer.update_sim(self.sim)
        obs = self.reset_model()
        self._set_action_space()
        # This is just a temp initialization, the final obs space will depend
        # on SelectKeysWrapper
        self.observation_space = spu.convert_obs_to_space(obs)
        self.metadata["video.frames_per_second"] = int(np.round(1.0 / self.dt))
        self.obs_temp = obs  ### what I added

        return obs

• hfield.py

class UnimalHeightObs(gym.ObservationWrapper):
    def __init__(self, env):
        super().__init__(env)
        self.observation_space = spu.update_obs_space(env, {"torso_height": (1,)})

    def observation(self, obs):
        obs = self.obs_temp   ### what I added
        x_pos, y_pos, z_pos = self.sim.data.get_body_xpos("torso/0")
   ........
   ........

After that, I got an error like below.

Process ForkProcess-3:
Traceback (most recent call last):
  File "/home/bak/Projects/metamorph/metamorph/envs/vec_env/subproc_vec_env.py", line 27, in worker
    remote.send([env.reset() for env in envs])
  File "/home/bak/Projects/metamorph/metamorph/envs/vec_env/subproc_vec_env.py", line 27, in <listcomp>
    remote.send([env.reset() for env in envs])
  File "/home/bak/Projects/metamorph/metamorph/envs/wrappers/multi_env_wrapper.py", line 40, in reset
    obs = self._env.reset()
  File "/home/bak/Projects/metamorph/metamorph/algos/ppo/envs.py", line 187, in reset
    observation = super(RecordEpisodeStatistics, self).reset(**kwargs)
  File "/home/bak/anaconda3/envs/metamorph/lib/python3.8/site-packages/gym/core.py", line 323, in reset
    return self.env.reset(**kwargs)
  File "/home/bak/Projects/metamorph/metamorph/algos/ppo/envs.py", line 169, in reset
    return self.env.reset(**kwargs)
  File "/home/bak/anaconda3/envs/metamorph/lib/python3.8/site-packages/gym/wrappers/time_limit.py", line 68, in reset
    return self.env.reset(**kwargs)
  File "/home/bak/anaconda3/envs/metamorph/lib/python3.8/site-packages/gym/wrappers/order_enforcing.py", line 42, in reset
    return self.env.reset(**kwargs)
  File "/home/bak/anaconda3/envs/metamorph/lib/python3.8/site-packages/gym/wrappers/env_checker.py", line 47, in reset
    return self.env.reset(**kwargs)
  File "/home/bak/anaconda3/envs/metamorph/lib/python3.8/site-packages/gym/core.py", line 379, in reset
    obs, info = self.env.reset(**kwargs)
ValueError: too many values to unpack (expected 2)

How can I fix these problems and check the result of your experiments?

I used Anaconda environment with mujoco-2.1.0 rather than Docker due to using free version of mujoco and using mujoco-py. Unfortunately, using mujoco after 2.1.0 does not support mujoco-py due to it has its own python binding.