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Zhongwei Li
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"""
Template for creating custom Gymnasium environments compatible with Stable Baselines3.
This template demonstrates:
- Proper Gymnasium environment structure
- Observation and action space definition
- Step and reset implementation
- Validation with SB3's env_checker
- Registration with Gymnasium
"""
import gymnasium as gym
from gymnasium import spaces
import numpy as np
class CustomEnv(gym.Env):
"""
Custom Gymnasium Environment Template.
This is a template for creating custom environments that work with
Stable Baselines3. Modify the observation space, action space, reward
function, and state transitions to match your specific problem.
Example:
A simple grid world where the agent tries to reach a goal position.
"""
# Optional: Provide metadata for rendering modes
metadata = {"render_modes": ["human", "rgb_array"], "render_fps": 30}
def __init__(self, grid_size=5, render_mode=None):
"""
Initialize the environment.
Args:
grid_size: Size of the grid world (grid_size x grid_size)
render_mode: How to render ('human', 'rgb_array', or None)
"""
super().__init__()
self.grid_size = grid_size
self.render_mode = render_mode
# Define action space
# Example: 4 discrete actions (up, down, left, right)
self.action_space = spaces.Discrete(4)
# Define observation space
# Example: 2D position [x, y] in continuous space
# Note: Use np.float32 for observations (SB3 recommendation)
self.observation_space = spaces.Box(
low=0,
high=grid_size - 1,
shape=(2,),
dtype=np.float32,
)
# Alternative observation spaces:
# 1. Discrete: spaces.Discrete(n)
# 2. Multi-discrete: spaces.MultiDiscrete([n1, n2, ...])
# 3. Multi-binary: spaces.MultiBinary(n)
# 4. Box (continuous): spaces.Box(low=, high=, shape=, dtype=np.float32)
# 5. Dict: spaces.Dict({"key1": space1, "key2": space2})
# For image observations (e.g., 84x84 RGB image):
# self.observation_space = spaces.Box(
# low=0,
# high=255,
# shape=(3, 84, 84), # (channels, height, width) - channel-first
# dtype=np.uint8,
# )
# Initialize state
self._agent_position = None
self._goal_position = None
def reset(self, seed=None, options=None):
"""
Reset the environment to initial state.
Args:
seed: Random seed for reproducibility
options: Additional options (optional)
Returns:
observation: Initial observation
info: Additional information dictionary
"""
# Set seed for reproducibility
super().reset(seed=seed)
# Initialize agent position randomly
self._agent_position = self.np_random.integers(0, self.grid_size, size=2)
# Initialize goal position (different from agent)
self._goal_position = self.np_random.integers(0, self.grid_size, size=2)
while np.array_equal(self._agent_position, self._goal_position):
self._goal_position = self.np_random.integers(0, self.grid_size, size=2)
observation = self._get_obs()
info = self._get_info()
return observation, info
def step(self, action):
"""
Execute one step in the environment.
Args:
action: Action to take
Returns:
observation: New observation
reward: Reward for this step
terminated: Whether episode has ended (goal reached)
truncated: Whether episode was truncated (time limit, etc.)
info: Additional information dictionary
"""
# Map action to direction (0: up, 1: down, 2: left, 3: right)
direction = np.array([
[-1, 0], # up
[1, 0], # down
[0, -1], # left
[0, 1], # right
])[action]
# Update agent position (clip to stay within grid)
self._agent_position = np.clip(
self._agent_position + direction,
0,
self.grid_size - 1,
)
# Check if goal is reached
terminated = np.array_equal(self._agent_position, self._goal_position)
# Calculate reward
if terminated:
reward = 1.0 # Goal reached
else:
# Negative reward based on distance to goal (encourages efficiency)
distance = np.linalg.norm(self._agent_position - self._goal_position)
reward = -0.1 * distance
# Episode not truncated in this example (no time limit)
truncated = False
observation = self._get_obs()
info = self._get_info()
return observation, reward, terminated, truncated, info
def _get_obs(self):
"""
Get current observation.
Returns:
observation: Current state as defined by observation_space
"""
# Return agent position as observation
return self._agent_position.astype(np.float32)
# For dict observations:
# return {
# "agent": self._agent_position.astype(np.float32),
# "goal": self._goal_position.astype(np.float32),
# }
def _get_info(self):
"""
Get additional information (for debugging/logging).
Returns:
info: Dictionary with additional information
"""
return {
"agent_position": self._agent_position,
"goal_position": self._goal_position,
"distance_to_goal": np.linalg.norm(
self._agent_position - self._goal_position
),
}
def render(self):
"""
Render the environment.
Returns:
Rendered frame (if render_mode is 'rgb_array')
"""
if self.render_mode == "human":
# Print simple text-based rendering
grid = np.zeros((self.grid_size, self.grid_size), dtype=str)
grid[:, :] = "."
grid[tuple(self._agent_position)] = "A"
grid[tuple(self._goal_position)] = "G"
print("\n" + "=" * (self.grid_size * 2 + 1))
for row in grid:
print(" ".join(row))
print("=" * (self.grid_size * 2 + 1) + "\n")
elif self.render_mode == "rgb_array":
# Return RGB array for video recording
# This is a placeholder - implement proper rendering as needed
canvas = np.zeros((
self.grid_size * 50,
self.grid_size * 50,
3
), dtype=np.uint8)
# Draw agent and goal on canvas
# ... (implement visual rendering)
return canvas
def close(self):
"""
Clean up environment resources.
"""
pass
# Optional: Register the environment with Gymnasium
# This allows creating the environment with gym.make("CustomEnv-v0")
gym.register(
id="CustomEnv-v0",
entry_point=__name__ + ":CustomEnv",
max_episode_steps=100,
)
def validate_environment():
"""
Validate the custom environment with SB3's env_checker.
"""
from stable_baselines3.common.env_checker import check_env
print("Validating custom environment...")
env = CustomEnv()
check_env(env, warn=True)
print("Environment validation passed!")
def test_environment():
"""
Test the custom environment with random actions.
"""
print("Testing environment with random actions...")
env = CustomEnv(render_mode="human")
obs, info = env.reset()
print(f"Initial observation: {obs}")
print(f"Initial info: {info}")
for step in range(10):
action = env.action_space.sample() # Random action
obs, reward, terminated, truncated, info = env.step(action)
print(f"\nStep {step + 1}:")
print(f" Action: {action}")
print(f" Observation: {obs}")
print(f" Reward: {reward:.3f}")
print(f" Terminated: {terminated}")
print(f" Info: {info}")
env.render()
if terminated or truncated:
print("Episode finished!")
break
env.close()
def train_on_custom_env():
"""
Train a PPO agent on the custom environment.
"""
from stable_baselines3 import PPO
print("Training PPO agent on custom environment...")
# Create environment
env = CustomEnv()
# Validate first
from stable_baselines3.common.env_checker import check_env
check_env(env, warn=True)
# Train agent
model = PPO("MlpPolicy", env, verbose=1)
model.learn(total_timesteps=10000)
# Test trained agent
obs, info = env.reset()
for _ in range(20):
action, _states = model.predict(obs, deterministic=True)
obs, reward, terminated, truncated, info = env.step(action)
if terminated or truncated:
print(f"Goal reached! Final reward: {reward}")
break
env.close()
if __name__ == "__main__":
# Validate the environment
validate_environment()
# Test with random actions
# test_environment()
# Train an agent
# train_on_custom_env()

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"""
Template script for evaluating trained RL agents with Stable Baselines3.
This template demonstrates:
- Loading trained models
- Evaluating performance with statistics
- Recording videos of agent behavior
- Visualizing agent performance
"""
import gymnasium as gym
import numpy as np
from stable_baselines3 import PPO
from stable_baselines3.common.evaluation import evaluate_policy
from stable_baselines3.common.vec_env import DummyVecEnv, VecVideoRecorder, VecNormalize
import os
def evaluate_agent(
model_path,
env_id="CartPole-v1",
n_eval_episodes=10,
deterministic=True,
render=False,
record_video=False,
video_folder="./videos/",
vec_normalize_path=None,
):
"""
Evaluate a trained RL agent.
Args:
model_path: Path to the saved model
env_id: Gymnasium environment ID
n_eval_episodes: Number of episodes to evaluate
deterministic: Use deterministic actions
render: Render the environment during evaluation
record_video: Record videos of the agent
video_folder: Folder to save videos
vec_normalize_path: Path to VecNormalize statistics (if used during training)
Returns:
mean_reward: Mean episode reward
std_reward: Standard deviation of episode rewards
"""
# Load the trained model
print(f"Loading model from {model_path}...")
model = PPO.load(model_path)
# Create evaluation environment
if render:
env = gym.make(env_id, render_mode="human")
else:
env = gym.make(env_id)
# Wrap in DummyVecEnv for consistency
env = DummyVecEnv([lambda: env])
# Load VecNormalize statistics if they were used during training
if vec_normalize_path and os.path.exists(vec_normalize_path):
print(f"Loading VecNormalize statistics from {vec_normalize_path}...")
env = VecNormalize.load(vec_normalize_path, env)
env.training = False # Don't update statistics during evaluation
env.norm_reward = False # Don't normalize rewards during evaluation
# Set up video recording if requested
if record_video:
os.makedirs(video_folder, exist_ok=True)
env = VecVideoRecorder(
env,
video_folder,
record_video_trigger=lambda x: x == 0, # Record all episodes
video_length=1000, # Max video length
name_prefix=f"eval-{env_id}",
)
print(f"Recording videos to {video_folder}...")
# Evaluate the agent
print(f"Evaluating for {n_eval_episodes} episodes...")
mean_reward, std_reward = evaluate_policy(
model,
env,
n_eval_episodes=n_eval_episodes,
deterministic=deterministic,
render=False, # VecEnv doesn't support render parameter
return_episode_rewards=False,
)
print(f"Mean reward: {mean_reward:.2f} +/- {std_reward:.2f}")
# Cleanup
env.close()
return mean_reward, std_reward
def watch_agent(
model_path,
env_id="CartPole-v1",
n_episodes=5,
deterministic=True,
vec_normalize_path=None,
):
"""
Watch a trained agent play (with rendering).
Args:
model_path: Path to the saved model
env_id: Gymnasium environment ID
n_episodes: Number of episodes to watch
deterministic: Use deterministic actions
vec_normalize_path: Path to VecNormalize statistics (if used during training)
"""
# Load the trained model
print(f"Loading model from {model_path}...")
model = PPO.load(model_path)
# Create environment with rendering
env = gym.make(env_id, render_mode="human")
# Load VecNormalize statistics if needed
obs_normalization = None
if vec_normalize_path and os.path.exists(vec_normalize_path):
print(f"Loading VecNormalize statistics from {vec_normalize_path}...")
# For rendering, we'll manually apply normalization
dummy_env = DummyVecEnv([lambda: gym.make(env_id)])
vec_env = VecNormalize.load(vec_normalize_path, dummy_env)
obs_normalization = vec_env
dummy_env.close()
# Run episodes
for episode in range(n_episodes):
obs, info = env.reset()
episode_reward = 0
done = False
step = 0
print(f"\nEpisode {episode + 1}/{n_episodes}")
while not done:
# Apply observation normalization if needed
if obs_normalization:
obs_normalized = obs_normalization.normalize_obs(obs)
else:
obs_normalized = obs
# Get action from model
action, _states = model.predict(obs_normalized, deterministic=deterministic)
# Take step in environment
obs, reward, terminated, truncated, info = env.step(action)
done = terminated or truncated
episode_reward += reward
step += 1
print(f"Episode reward: {episode_reward:.2f} ({step} steps)")
env.close()
def compare_models(
model_paths,
env_id="CartPole-v1",
n_eval_episodes=10,
deterministic=True,
):
"""
Compare performance of multiple trained models.
Args:
model_paths: List of paths to saved models
env_id: Gymnasium environment ID
n_eval_episodes: Number of episodes to evaluate each model
deterministic: Use deterministic actions
"""
results = {}
for model_path in model_paths:
print(f"\nEvaluating {model_path}...")
mean_reward, std_reward = evaluate_agent(
model_path,
env_id=env_id,
n_eval_episodes=n_eval_episodes,
deterministic=deterministic,
)
results[model_path] = {"mean": mean_reward, "std": std_reward}
# Print comparison
print("\n" + "=" * 60)
print("Model Comparison Results")
print("=" * 60)
for model_path, stats in results.items():
print(f"{model_path}: {stats['mean']:.2f} +/- {stats['std']:.2f}")
print("=" * 60)
return results
if __name__ == "__main__":
# Example 1: Evaluate a trained model
model_path = "./models/best_model/best_model.zip"
evaluate_agent(
model_path=model_path,
env_id="CartPole-v1",
n_eval_episodes=10,
deterministic=True,
)
# Example 2: Record videos of agent behavior
# evaluate_agent(
# model_path=model_path,
# env_id="CartPole-v1",
# n_eval_episodes=5,
# deterministic=True,
# record_video=True,
# video_folder="./videos/",
# )
# Example 3: Watch agent play with rendering
# watch_agent(
# model_path=model_path,
# env_id="CartPole-v1",
# n_episodes=3,
# deterministic=True,
# )
# Example 4: Compare multiple models
# compare_models(
# model_paths=[
# "./models/model_100k.zip",
# "./models/model_200k.zip",
# "./models/best_model/best_model.zip",
# ],
# env_id="CartPole-v1",
# n_eval_episodes=10,
# )
# Example 5: Evaluate with VecNormalize statistics
# evaluate_agent(
# model_path="./models/best_model/best_model.zip",
# env_id="Pendulum-v1",
# n_eval_episodes=10,
# vec_normalize_path="./models/vec_normalize.pkl",
# )

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"""
Template script for training RL agents with Stable Baselines3.
This template demonstrates best practices for:
- Setting up training with proper monitoring
- Using callbacks for evaluation and checkpointing
- Vectorized environments for efficiency
- TensorBoard integration
- Model saving and loading
"""
import gymnasium as gym
from stable_baselines3 import PPO
from stable_baselines3.common.env_util import make_vec_env
from stable_baselines3.common.callbacks import (
EvalCallback,
CheckpointCallback,
CallbackList,
)
from stable_baselines3.common.vec_env import SubprocVecEnv, VecNormalize
import os
def train_agent(
env_id="CartPole-v1",
algorithm=PPO,
policy="MlpPolicy",
n_envs=4,
total_timesteps=100000,
eval_freq=10000,
save_freq=10000,
log_dir="./logs/",
save_path="./models/",
):
"""
Train an RL agent with best practices.
Args:
env_id: Gymnasium environment ID
algorithm: SB3 algorithm class (PPO, SAC, DQN, etc.)
policy: Policy type ("MlpPolicy", "CnnPolicy", "MultiInputPolicy")
n_envs: Number of parallel environments
total_timesteps: Total training timesteps
eval_freq: Frequency of evaluation (in timesteps)
save_freq: Frequency of model checkpoints (in timesteps)
log_dir: Directory for logs and TensorBoard
save_path: Directory for model checkpoints
"""
# Create directories
os.makedirs(log_dir, exist_ok=True)
os.makedirs(save_path, exist_ok=True)
eval_log_dir = os.path.join(log_dir, "eval")
os.makedirs(eval_log_dir, exist_ok=True)
# Create training environment (vectorized for efficiency)
print(f"Creating {n_envs} parallel training environments...")
env = make_vec_env(
env_id,
n_envs=n_envs,
vec_env_cls=SubprocVecEnv, # Use SubprocVecEnv for parallel execution
# vec_env_cls=DummyVecEnv, # Use DummyVecEnv for lightweight environments
)
# Optional: Add normalization wrapper for better performance
# Uncomment for continuous control tasks
# env = VecNormalize(env, norm_obs=True, norm_reward=True, clip_obs=10.0)
# Create separate evaluation environment
print("Creating evaluation environment...")
eval_env = make_vec_env(env_id, n_envs=1)
# If using VecNormalize, wrap eval env but set training=False
# eval_env = VecNormalize(eval_env, training=False, norm_reward=False)
# Set up callbacks
eval_callback = EvalCallback(
eval_env,
best_model_save_path=os.path.join(save_path, "best_model"),
log_path=eval_log_dir,
eval_freq=eval_freq // n_envs, # Adjust for number of environments
n_eval_episodes=10,
deterministic=True,
render=False,
)
checkpoint_callback = CheckpointCallback(
save_freq=save_freq // n_envs, # Adjust for number of environments
save_path=save_path,
name_prefix="rl_model",
save_replay_buffer=False, # Set True for off-policy algorithms if needed
)
callback = CallbackList([eval_callback, checkpoint_callback])
# Initialize the agent
print(f"Initializing {algorithm.__name__} agent...")
model = algorithm(
policy,
env,
verbose=1,
tensorboard_log=log_dir,
# Algorithm-specific hyperparameters can be added here
# learning_rate=3e-4,
# n_steps=2048, # For PPO/A2C
# batch_size=64,
# gamma=0.99,
)
# Train the agent
print(f"Training for {total_timesteps} timesteps...")
model.learn(
total_timesteps=total_timesteps,
callback=callback,
tb_log_name=f"{algorithm.__name__}_{env_id}",
)
# Save final model
final_model_path = os.path.join(save_path, "final_model")
print(f"Saving final model to {final_model_path}...")
model.save(final_model_path)
# Save VecNormalize statistics if used
# env.save(os.path.join(save_path, "vec_normalize.pkl"))
print("Training complete!")
print(f"Best model saved at: {os.path.join(save_path, 'best_model')}")
print(f"Final model saved at: {final_model_path}")
print(f"TensorBoard logs: {log_dir}")
print(f"Run 'tensorboard --logdir {log_dir}' to view training progress")
# Cleanup
env.close()
eval_env.close()
return model
if __name__ == "__main__":
# Example: Train PPO on CartPole
train_agent(
env_id="CartPole-v1",
algorithm=PPO,
policy="MlpPolicy",
n_envs=4,
total_timesteps=100000,
)
# Example: Train SAC on continuous control task
# from stable_baselines3 import SAC
# train_agent(
# env_id="Pendulum-v1",
# algorithm=SAC,
# policy="MlpPolicy",
# n_envs=4,
# total_timesteps=50000,
# )
# Example: Train DQN on discrete task
# from stable_baselines3 import DQN
# train_agent(
# env_id="LunarLander-v2",
# algorithm=DQN,
# policy="MlpPolicy",
# n_envs=1, # DQN typically uses single env
# total_timesteps=100000,
# )