Add VectorizeMode enum for make_vec(..., vectorization_mode)

gymnasium/__init__.py

@@ -16,6 +16,7 @@
     registry,
     pprint_registry,
     make_vec,
+    VectorizeMode,
     register_envs,
 )
 
@@ -38,6 +39,7 @@
     "spec",
     "register",
     "registry",
+    "VectorizeMode",
     "pprint_registry",
     "register_envs",
     # module folders

gymnasium/envs/registration.py

@@ -12,6 +12,7 @@
 import sys
 from collections import defaultdict
 from dataclasses import dataclass, field
+from enum import Enum
 from types import ModuleType
 from typing import Any, Callable, Iterable, Sequence
 
@@ -37,6 +38,7 @@
     "current_namespace",
     "EnvSpec",
     "WrapperSpec",
+    "VectorizeMode",
     # Functions
     "register",
     "make",
@@ -57,7 +59,7 @@ def __call__(self, **kwargs: Any) -> Env:
 class VectorEnvCreator(Protocol):
     """Function type expected for an environment."""
 
-    def __call__(self, **kwargs: Any) -> gym.experimental.vector.VectorEnv:
+    def __call__(self, **kwargs: Any) -> gym.vector.VectorEnv:
         ...
 
 
@@ -249,6 +251,14 @@ def pprint(
             print(output)
 
 
+class VectorizeMode(Enum):
+    """All possible vectorization modes used in `make_vec`."""
+
+    ASYNC = "async"
+    SYNC = "sync"
+    VECTOR_ENTRY_POINT = "vector_entry_point"
+
+
 # Global registry of environments. Meant to be accessed through `register` and `make`
 registry: dict[str, EnvSpec] = {}
 current_namespace: str | None = None
@@ -809,7 +819,7 @@ def make(
 def make_vec(
     id: str | EnvSpec,
     num_envs: int = 1,
-    vectorization_mode: str | None = None,
+    vectorization_mode: VectorizeMode | str | None = None,
     vector_kwargs: dict[str, Any] | None = None,
     wrappers: Sequence[Callable[[Env], Wrapper]] | None = None,
     **kwargs,
@@ -822,9 +832,9 @@ def make_vec(
     Args:
         id: Name of the environment. Optionally, a module to import can be included, eg. 'module:Env-v0'
         num_envs: Number of environments to create
-        vectorization_mode: The vectorization method used, defaults to ``None`` such that if a ``vector_entry_point`` exists,
+        vectorization_mode: The vectorization method used, defaults to ``None`` such that if env id' spec has a ``vector_entry_point`` (not ``None``),
             this is first used otherwise defaults to ``sync`` to use the :class:`gymnasium.vector.SyncVectorEnv`.
-            Valid modes are ``"async"``, ``"sync"`` or ``"vector_entry_point"``.
+            Valid modes are ``"async"``, ``"sync"`` or ``"vector_entry_point"``. Recommended to use the :class:`VectorizeMode` enum rather than strings.
         vector_kwargs: Additional arguments to pass to the vectorizor environment constructor, i.e., ``SyncVectorEnv(..., **vector_kwargs)``.
         wrappers: A sequence of wrapper functions to apply to the base environment. Can only be used in ``"sync"`` or ``"async"`` mode.
         **kwargs: Additional arguments passed to the base environment constructor.
@@ -856,12 +866,21 @@ def make_vec(
 
     env_spec_kwargs.update(kwargs)
 
-    # Update the vectorization_mode if None
+    # Specify the vectorization mode if None or update to a `VectorizeMode`
     if vectorization_mode is None:
         if id_env_spec.vector_entry_point is not None:
-            vectorization_mode = "vector_entry_point"
+            vectorization_mode = VectorizeMode.VECTOR_ENTRY_POINT
         else:
-            vectorization_mode = "sync"
+            vectorization_mode = VectorizeMode.SYNC
+    else:
+        try:
+            vectorization_mode = VectorizeMode(vectorization_mode)
+        except ValueError:
+            raise ValueError(
+                f"Invalid vectorization mode: {vectorization_mode!r}, "
+                f"valid modes: {[mode.value for mode in VectorizeMode]}"
+            )
+    assert isinstance(vectorization_mode, VectorizeMode)
 
     def create_single_env() -> Env:
         single_env = make(id_env_spec.id, **env_spec_kwargs.copy())
@@ -870,7 +889,7 @@ def create_single_env() -> Env:
             single_env = wrapper(single_env)
         return single_env
 
-    if vectorization_mode == "sync":
+    if vectorization_mode == VectorizeMode.SYNC:
         if id_env_spec.entry_point is None:
             raise error.Error(
                 f"Cannot create vectorized environment for {id_env_spec.id} because it doesn't have an entry point defined."
@@ -880,7 +899,7 @@ def create_single_env() -> Env:
             env_fns=(create_single_env for _ in range(num_envs)),
             **vector_kwargs,
         )
-    elif vectorization_mode == "async":
+    elif vectorization_mode == VectorizeMode.ASYNC:
         if id_env_spec.entry_point is None:
             raise error.Error(
                 f"Cannot create vectorized environment for {id_env_spec.id} because it doesn't have an entry point defined."
@@ -890,7 +909,7 @@ def create_single_env() -> Env:
             env_fns=[create_single_env for _ in range(num_envs)],
             **vector_kwargs,
         )
-    elif vectorization_mode == "vector_entry_point":
+    elif vectorization_mode == VectorizeMode.VECTOR_ENTRY_POINT:
         entry_point = id_env_spec.vector_entry_point
         if entry_point is None:
             raise error.Error(
@@ -910,15 +929,14 @@ def create_single_env() -> Env:
 
         env = env_creator(num_envs=num_envs, **vector_kwargs)
     else:
-        raise error.Error(f"Invalid vectorization mode: {vectorization_mode}")
+        raise error.Error(f"Unknown vectorization mode: {vectorization_mode}")
 
     # Copies the environment creation specification and kwargs to add to the environment specification details
     copied_id_spec = copy.deepcopy(id_env_spec)
     copied_id_spec.kwargs = env_spec_kwargs
     if num_envs != 1:
         copied_id_spec.kwargs["num_envs"] = num_envs
-    if vectorization_mode != "async":
-        copied_id_spec.kwargs["vectorization_mode"] = vectorization_mode
+    copied_id_spec.kwargs["vectorization_mode"] = vectorization_mode.value
     if vector_kwargs is not None:
         copied_id_spec.kwargs["vector_kwargs"] = vector_kwargs
     if wrappers is not None:

tests/envs/registration/test_make_vec.py

@@ -4,6 +4,7 @@
 import pytest
 
 import gymnasium as gym
+from gymnasium import VectorizeMode
 from gymnasium.envs.classic_control import CartPoleEnv
 from gymnasium.envs.classic_control.cartpole import CartPoleVectorEnv
 from gymnasium.vector import AsyncVectorEnv, SyncVectorEnv
@@ -45,11 +46,17 @@ def test_make_vec_vectorization_mode():
     assert isinstance(env, SyncVectorEnv)
     env.close()
 
-    # Test `vector_entry_point`
+    # Test `vector_entry_point` for env specs with and without it
     env = gym.make_vec("CartPole-v1", vectorization_mode="vector_entry_point")
     assert isinstance(env, CartPoleVectorEnv)
     env.close()
 
+    env = gym.make_vec(
+        "CartPole-v1", vectorization_mode=VectorizeMode.VECTOR_ENTRY_POINT
+    )
+    assert isinstance(env, CartPoleVectorEnv)
+    env.close()
+
     with pytest.raises(
         gym.error.Error,
         match=re.escape(
@@ -58,12 +65,28 @@ def test_make_vec_vectorization_mode():
     ):
         gym.make_vec("Pendulum-v1", vectorization_mode="vector_entry_point")
 
-    # Test `async`
+    # Test `async` and `sync`
     env = gym.make_vec("CartPole-v1", vectorization_mode="async")
     assert isinstance(env, AsyncVectorEnv)
     env.close()
 
+    env = gym.make_vec("CartPole-v1", vectorization_mode=VectorizeMode.ASYNC)
+    assert isinstance(env, AsyncVectorEnv)
+    env.close()
+
+    env = gym.make_vec("CartPole-v1", vectorization_mode="sync")
+    assert isinstance(env, SyncVectorEnv)
+    env.close()
+
+    env = gym.make_vec("CartPole-v1", vectorization_mode=VectorizeMode.SYNC)
+    assert isinstance(env, SyncVectorEnv)
+    env.close()
+
+    # Test environment with only a vector entry point and no entry point
     gym.register("VecOnlyEnv-v0", vector_entry_point=CartPoleVectorEnv)
+    env_spec = gym.spec("VecOnlyEnv-v0")
+    assert env_spec.entry_point is None and env_spec.vector_entry_point is not None
+
     with pytest.raises(
         gym.error.Error,
         match=re.escape(
@@ -73,9 +96,22 @@ def test_make_vec_vectorization_mode():
         gym.make_vec("VecOnlyEnv-v0", vectorization_mode="async")
     del gym.registry["VecOnlyEnv-v0"]
 
-    env = gym.make_vec("CartPole-v1", vectorization_mode="sync")
-    assert isinstance(env, SyncVectorEnv)
-    env.close()
+    # Test with invalid vectorization mode
+    with pytest.raises(
+        ValueError,
+        match=re.escape(
+            "Invalid vectorization mode: 'invalid', valid modes: ['async', 'sync', 'vector_entry_point']"
+        ),
+    ):
+        gym.make_vec("CartPole-v1", vectorization_mode="invalid")
+
+    with pytest.raises(
+        ValueError,
+        match=re.escape(
+            "Invalid vectorization mode: 123, valid modes: ['async', 'sync', 'vector_entry_point']"
+        ),
+    ):
+        gym.make_vec("CartPole-v1", vectorization_mode=123)
 
 
 def test_make_vec_wrappers():