Gymnasium/docs/content/gym_compatibility.md

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contents	Compatibility With Gym

Compatibility with Gym

Gymnasium provides a number of compatibility methods for a range of Environment implementations.

Loading OpenAI Gym environments

.. py:currentmodule:: gymnasium.wrappers

For environments that are registered solely in OpenAI Gym and not in Gymnasium, Gymnasium v0.26.3 and above allows importing them through either a special environment or a wrapper.
The ``"GymV26Environment-v0"`` environment was introduced in Gymnasium v0.26.3, and allows importing of Gym environments through the ``env_name`` argument along with other relevant kwargs environment kwargs.
To perform conversion through a wrapper, the environment itself can be passed to the wrapper :class:`EnvCompatibility` through the ``env`` kwarg.

An example of this is atari 0.8.0 which does not have a gymnasium implementation.

import gymnasium as gym

env = gym.make("GymV26Environment-v0", env_id="ALE/Pong-v5")

Gym v0.21 Environment Compatibility

.. py:currentmodule:: gymnasium

A number of environments have not updated to the recent Gym changes, in particular since v0.21.
This update is significant for the introduction of ``termination`` and ``truncation`` signatures in favour of the previously used ``done``.
To allow backward compatibility, Gym and Gymnasium v0.26+ include an ``apply_api_compatibility`` kwarg when calling :meth:`make` that automatically converts a v0.21 API compliant environment to one that is compatible with v0.26+.

import gym

env = gym.make("OldV21Env-v0", apply_api_compatibility=True)

Additionally, in Gymnasium we provide specialist environments for compatibility that for env_id will call gym.make.

import gymnasium

env = gymnasium.make("GymV21Environment-v0", env_id="CartPole-v1", render_mode="human")
# or
env = gymnasium.make("GymV21Environment-v0", env=OldV21Env())

Step API Compatibility

If environments implement the (old) done step API, Gymnasium provides both functions (:meth:`gymnasium.utils.step_api_compatibility.convert_to_terminated_truncated_step_api`) and wrappers (:class:`gymnasium.wrappers.StepAPICompatibility`) that will convert an environment with the old step API (using ``done``) to the new step API (using ``termination`` and ``truncation``).