DQN训练atari游戏：No module named ‘atari_py‘

安装好 gym 后，加载《太空入侵者》游戏。

import gym
env = gym.make('SpaceInvaders-v0')

出现下面的问题：

Traceback (most recent call last):
  File "/home/jacob/anaconda3/envs/python37/lib/python3.7/site-packages/gym/envs/atari/atari_env.py", line 9, in <module>
    import atari_py
ModuleNotFoundError: No module named 'atari_py'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<frozen importlib._bootstrap>", line 983, in _find_and_load
  File "<frozen importlib._bootstrap>", line 967, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 677, in _load_unlocked
  File "<frozen importlib._bootstrap_external>", line 728, in exec_module
  File "<frozen importlib._bootstrap>", line 219, in _call_with_frames_removed
  File "/home/jacob/anaconda3/envs/python37/lib/python3.7/site-packages/gym/envs/atari/__init__.py", line 1, in <module>
    from gym.envs.atari.atari_env import AtariEnv
  File "/home/jacob/anaconda3/envs/python37/lib/python3.7/site-packages/gym/envs/atari/atari_env.py", line 13, in <module>
    "'pip install gym[atari]'.)".format(e))
gym.error.DependencyNotInstalled: No module named 'atari_py'. (HINT: you can install Atari dependencies by running 'pip install gym[atari]'.)

解决方法：根据报错提示，使用了下面的代码安装，已成功。这里使用了国内源，安装更快。

pip install gym[atari] -i https://pypi.tuna.tsinghua.edu.cn/simple