Source code for gymnasium.wrappers.transform_reward
"""Wrapper for transforming the reward."""
from typing import Callable
import gymnasium as gym
[docs]class TransformReward(gym.RewardWrapper, gym.utils.RecordConstructorArgs):
"""Transform the reward via an arbitrary function.
Warning:
If the base environment specifies a reward range which is not invariant under :attr:`f`, the :attr:`reward_range` of the wrapped environment will be incorrect.
Example:
>>> import gymnasium as gym
>>> from gymnasium.wrappers import TransformReward
>>> env = gym.make("CartPole-v1")
>>> env = TransformReward(env, lambda r: 0.01*r)
>>> _ = env.reset()
>>> observation, reward, terminated, truncated, info = env.step(env.action_space.sample())
>>> reward
0.01
"""
def __init__(self, env: gym.Env, f: Callable[[float], float]):
"""Initialize the :class:`TransformReward` wrapper with an environment and reward transform function :attr:`f`.
Args:
env: The environment to apply the wrapper
f: A function that transforms the reward
"""
gym.utils.RecordConstructorArgs.__init__(self, f=f)
gym.RewardWrapper.__init__(self, env)
assert callable(f)
self.f = f
def reward(self, reward):
"""Transforms the reward using callable :attr:`f`.
Args:
reward: The reward to transform
Returns:
The transformed reward
"""
return self.f(reward)