removed calls to reset from init (#2394)

* removed all calls to reset

* passing tests

* fix off-by-one error

* revert

* merge master into branch

* add OrderEnforcing Wrapper

* add orderenforcing to the docs

* add option for disabling

* add argument to EnvSpec

docs/wrappers.md

@@ -141,4 +141,15 @@ Lastly the `name_prefix` allows you to customize the name of the videos.
 `TimeLimit(env, max_episode_steps)` [text]
 * Needs review (including for good assertion messages and test coverage)
 
+`OrderEnforcing(env)` [text]
+
+`OrderEnforcing` is a light-weight wrapper that throws an exception when `env.step()` is called before `env.reset()`, the wrapper is enabled by default for environment specs without `max_episode_steps` and can be disabled by passing `order_enforce=False` like:
+```python3
+register(
+    id="CustomEnv-v1",
+    entry_point="...",
+    order_enforce=False,
+)
+```
+
 Some sort of vector environment conversion wrapper needs to be added here, this will be figured out after the API is changed.

gym/envs/box2d/bipedal_walker.py

@@ -142,8 +142,6 @@ class BipedalWalker(gym.Env, EzPickle):
             categoryBits=0x0001,
         )
 
-        self.reset()
-
         high = np.array([np.inf] * 24).astype(np.float32)
         self.action_space = spaces.Box(
             np.array([-1, -1, -1, -1]).astype(np.float32),

gym/envs/box2d/lunar_lander.py

@@ -117,8 +117,6 @@ class LunarLander(gym.Env, EzPickle):
             # Nop, fire left engine, main engine, right engine
             self.action_space = spaces.Discrete(4)
 
-        self.reset()
-
     def seed(self, seed=None):
         self.np_random, seed = seeding.np_random(seed)
         return [seed]

gym/envs/classic_control/continuous_mountain_car.py

@@ -85,7 +85,6 @@ class Continuous_MountainCarEnv(gym.Env):
         )
 
         self.seed()
-        self.reset()
 
     def seed(self, seed=None):
         self.np_random, seed = seeding.np_random(seed)

gym/envs/registration.py

@@ -40,6 +40,7 @@ class EnvSpec(object):
         reward_threshold (Optional[int]): The reward threshold before the task is considered solved
         nondeterministic (bool): Whether this environment is non-deterministic even after seeding
         max_episode_steps (Optional[int]): The maximum number of steps that an episode can consist of
+        order_enforce (Optional[int]): Whether to wrap the environment in an orderEnforcing wrapper
         kwargs (dict): The kwargs to pass to the environment class
 
     """
@@ -51,6 +52,7 @@ class EnvSpec(object):
         reward_threshold=None,
         nondeterministic=False,
         max_episode_steps=None,
+        order_enforce=True,
         kwargs=None,
     ):
         self.id = id
@@ -58,6 +60,7 @@ class EnvSpec(object):
         self.reward_threshold = reward_threshold
         self.nondeterministic = nondeterministic
         self.max_episode_steps = max_episode_steps
+        self.order_enforce = order_enforce
         self._kwargs = {} if kwargs is None else kwargs
 
         match = env_id_re.search(id)
@@ -77,8 +80,10 @@ class EnvSpec(object):
                     self.id
                 )
             )
+
         _kwargs = self._kwargs.copy()
         _kwargs.update(kwargs)
+
         if callable(self.entry_point):
             env = self.entry_point(**_kwargs)
         else:
@@ -89,7 +94,15 @@ class EnvSpec(object):
         spec = copy.deepcopy(self)
         spec._kwargs = _kwargs
         env.unwrapped.spec = spec
+        if env.spec.max_episode_steps is not None:
+            from gym.wrappers.time_limit import TimeLimit
 
+            env = TimeLimit(env, max_episode_steps=env.spec.max_episode_steps)
+        else:
+            if self.order_enforce:
+                from gym.wrappers.order_enforcing import OrderEnforcing
+
+                env = OrderEnforcing(env)
         return env
 
     def __repr__(self):
@@ -115,10 +128,6 @@ class EnvRegistry(object):
             logger.info("Making new env: %s", path)
         spec = self.spec(path)
         env = spec.make(**kwargs)
-        if env.spec.max_episode_steps is not None:
-            from gym.wrappers.time_limit import TimeLimit
-
-            env = TimeLimit(env, max_episode_steps=env.spec.max_episode_steps)
         return env
 
     def all(self):

gym/envs/toy_text/blackjack.py

@@ -86,8 +86,6 @@ class BlackjackEnv(gym.Env):
 
         # Flag for full agreement with the (Sutton and Barto, 2018) definition. Overrides self.natural
         self.sab = sab
-        # Start the first game
-        self.reset()
 
     def seed(self, seed=None):
         self.np_random, seed = seeding.np_random(seed)

gym/utils/env_checker.py

@@ -300,10 +300,14 @@ def check_env(env: gym.Env, warn: bool = True, skip_render_check: bool = True) -
 
     # ============= Check the spaces (observation and action) ================
     _check_spaces(env)
-
     # Define aliases for convenience
     observation_space = env.observation_space
     action_space = env.action_space
+    try:
+        env.step(env.action_space.sample())
+
+    except AssertionError as e:
+        assert str(e) == "Cannot call env.step() before calling reset()"
 
     # Warn the user if needed.
     # A warning means that the environment may run but not work properly with popular RL libraries.

gym/wrappers/order_enforcing.py

@@ -0,0 +1,16 @@
+import gym
+
+
+class OrderEnforcing(gym.Wrapper):
+    def __init__(self, env):
+        super(OrderEnforcing, self).__init__(env)
+        self._has_reset = False
+
+    def step(self, action):
+        assert self._has_reset, "Cannot call env.step() before calling reset()"
+        observation, reward, done, info = self.env.step(action)
+        return observation, reward, done, info
+
+    def reset(self, **kwargs):
+        self._has_reset = True
+        return self.env.reset(**kwargs)

gym/wrappers/test_record_video.py

@@ -11,6 +11,7 @@ from gym.wrappers import (
 
 
 def test_record_video_using_default_trigger():
+
     env = gym.make("CartPole-v1")
     env = gym.wrappers.RecordVideo(env, "videos")
     env.reset()
@@ -66,7 +67,7 @@ def test_record_video_within_vector():
         _, _, _, infos = envs.step(envs.action_space.sample())
         for info in infos:
             if "episode" in info.keys():
-                print(f"i, episode_reward={info['episode']['r']}")
+                print(f"episode_reward={info['episode']['r']}")
                 break
     assert os.path.isdir("videos")
     mp4_files = [file for file in os.listdir("videos") if file.endswith(".mp4")]