Simplify code since loky is a dependency.

CHANGES.md

@@ -5,6 +5,10 @@ chronological order. Releases follow [semantic versioning](https://semver.org/)
 releases are available on [PyPI](https://pypi.org/project/pytask-parallel) and
 [Anaconda.org](https://anaconda.org/conda-forge/pytask-parallel).
 
+## 0.4.2 - 2024-xx-xx
+
+- {pull}`85` simplifies code since loky is a dependency.
+
 ## 0.4.1 - 2024-01-12
 
 - {pull}`72` moves the project to `pyproject.toml`.

src/pytask_parallel/backends.py

@@ -2,14 +2,15 @@
 
 from __future__ import annotations
 
-import enum
 from concurrent.futures import Future
 from concurrent.futures import ProcessPoolExecutor
 from concurrent.futures import ThreadPoolExecutor
+from enum import Enum
 from typing import Any
 from typing import Callable
 
 import cloudpickle
+from loky import get_reusable_executor
 
 
 def deserialize_and_run_with_cloudpickle(fn: bytes, kwargs: bytes) -> Any:
@@ -37,37 +38,16 @@ def submit(  # type: ignore[override]
         )
 
 
-try:
-    from loky import get_reusable_executor
+class ParallelBackend(Enum):
+    """Choices for parallel backends."""
 
-except ImportError:
+    PROCESSES = "processes"
+    THREADS = "threads"
+    LOKY = "loky"
 
-    class ParallelBackend(enum.Enum):
-        """Choices for parallel backends."""
 
-        PROCESSES = "processes"
-        THREADS = "threads"
-
-    PARALLEL_BACKENDS_DEFAULT = ParallelBackend.PROCESSES
-
-    PARALLEL_BACKENDS = {
-        ParallelBackend.PROCESSES: CloudpickleProcessPoolExecutor,
-        ParallelBackend.THREADS: ThreadPoolExecutor,
-    }
-
-else:
-
-    class ParallelBackend(enum.Enum):  # type: ignore[no-redef]
-        """Choices for parallel backends."""
-
-        PROCESSES = "processes"
-        THREADS = "threads"
-        LOKY = "loky"
-
-    PARALLEL_BACKENDS_DEFAULT = ParallelBackend.LOKY  # type: ignore[attr-defined]
-
-    PARALLEL_BACKENDS = {
-        ParallelBackend.PROCESSES: CloudpickleProcessPoolExecutor,
-        ParallelBackend.THREADS: ThreadPoolExecutor,
-        ParallelBackend.LOKY: get_reusable_executor,  # type: ignore[attr-defined]
-    }
+PARALLEL_BACKEND_BUILDER = {
+    ParallelBackend.PROCESSES: lambda: CloudpickleProcessPoolExecutor,
+    ParallelBackend.THREADS: lambda: ThreadPoolExecutor,
+    ParallelBackend.LOKY: lambda: get_reusable_executor,
+}

src/pytask_parallel/build.py

@@ -6,7 +6,6 @@
 from pytask import EnumChoice
 from pytask import hookimpl
 
-from pytask_parallel.backends import PARALLEL_BACKENDS_DEFAULT
 from pytask_parallel.backends import ParallelBackend
 
 
@@ -27,7 +26,7 @@ def pytask_extend_command_line_interface(cli: click.Group) -> None:
             ["--parallel-backend"],
             type=EnumChoice(ParallelBackend),
             help="Backend for the parallelization.",
-            default=PARALLEL_BACKENDS_DEFAULT,
+            default=ParallelBackend.LOKY,
         ),
     ]
     cli.commands["build"].params.extend(additional_parameters)

src/pytask_parallel/execute.py

@@ -34,7 +34,7 @@
 from pytask.tree_util import tree_structure
 from rich.traceback import Traceback
 
-from pytask_parallel.backends import PARALLEL_BACKENDS
+from pytask_parallel.backends import PARALLEL_BACKEND_BUILDER
 from pytask_parallel.backends import ParallelBackend
 
 if TYPE_CHECKING:
@@ -54,6 +54,12 @@ def pytask_post_parse(config: dict[str, Any]) -> None:
     else:
         config["pm"].register(ProcessesNameSpace)
 
+    if PARALLEL_BACKEND_BUILDER[config["parallel_backend"]] is None:
+        raise
+        config["_parallel_executor"] = PARALLEL_BACKEND_BUILDER[
+            config["parallel_backend"]
+        ]()
+
 
 @hookimpl(tryfirst=True)
 def pytask_execute_build(session: Session) -> bool | None:  # noqa: C901, PLR0915
@@ -73,7 +79,9 @@ def pytask_execute_build(session: Session) -> bool | None:  # noqa: C901, PLR091
         reports = session.execution_reports
         running_tasks: dict[str, Future[Any]] = {}
 
-        parallel_backend = PARALLEL_BACKENDS[session.config["parallel_backend"]]
+        parallel_backend = PARALLEL_BACKEND_BUILDER[
+            session.config["parallel_backend"]
+        ]()
 
         with parallel_backend(max_workers=session.config["n_workers"]) as executor:
             session.config["_parallel_executor"] = executor

tests/test_execute.py

@@ -7,7 +7,6 @@
 from pytask import ExitCode
 from pytask import build
 from pytask import cli
-from pytask_parallel.backends import PARALLEL_BACKENDS
 from pytask_parallel.backends import ParallelBackend
 from pytask_parallel.execute import _Sleeper
 
@@ -19,18 +18,18 @@ class Session:
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_parallel_execution(tmp_path, parallel_backend):
     source = """
-    import pytask
+    from pytask import Product
+    from pathlib import Path
+    from typing_extensions import Annotated
 
-    @pytask.mark.produces("out_1.txt")
-    def task_1(produces):
-        produces.write_text("1")
+    def task_1(path: Annotated[Path, Product] = Path("out_1.txt")):
+        path.write_text("1")
 
-    @pytask.mark.produces("out_2.txt")
-    def task_2(produces):
-        produces.write_text("2")
+    def task_2(path: Annotated[Path, Product] = Path("out_2.txt")):
+        path.write_text("2")
     """
     tmp_path.joinpath("task_example.py").write_text(textwrap.dedent(source))
     session = build(paths=tmp_path, n_workers=2, parallel_backend=parallel_backend)
@@ -41,18 +40,18 @@ def task_2(produces):
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_parallel_execution_w_cli(runner, tmp_path, parallel_backend):
     source = """
-    import pytask
+    from pytask import Product
+    from pathlib import Path
+    from typing_extensions import Annotated
 
-    @pytask.mark.produces("out_1.txt")
-    def task_1(produces):
-        produces.write_text("1")
+    def task_1(path: Annotated[Path, Product] = Path("out_1.txt")):
+        path.write_text("1")
 
-    @pytask.mark.produces("out_2.txt")
-    def task_2(produces):
-        produces.write_text("2")
+    def task_2(path: Annotated[Path, Product] = Path("out_2.txt")):
+        path.write_text("2")
     """
     tmp_path.joinpath("task_example.py").write_text(textwrap.dedent(source))
     result = runner.invoke(
@@ -71,7 +70,7 @@ def task_2(produces):
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_stop_execution_when_max_failures_is_reached(tmp_path, parallel_backend):
     source = """
     import time
@@ -99,7 +98,7 @@ def task_3(): time.sleep(3)
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_task_priorities(tmp_path, parallel_backend):
     source = """
     import pytask
@@ -140,7 +139,7 @@ def task_5():
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 @pytest.mark.parametrize("show_locals", [True, False])
 def test_rendering_of_tracebacks_with_rich(
     runner, tmp_path, parallel_backend, show_locals
@@ -173,12 +172,12 @@ def task_raising_error():
 )
 def test_collect_warnings_from_parallelized_tasks(runner, tmp_path, parallel_backend):
     source = """
-    import pytask
+    from pytask import task
     import warnings
 
     for i in range(2):
 
-        @pytask.mark.task(id=str(i), kwargs={"produces": f"{i}.txt"})
+        @task(id=str(i), kwargs={"produces": f"{i}.txt"})
         def task_example(produces):
             warnings.warn("This is a warning.")
             produces.touch()
@@ -222,7 +221,7 @@ def test_sleeper():
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_task_that_return(runner, tmp_path, parallel_backend):
     source = """
     from pathlib import Path
@@ -242,7 +241,7 @@ def task_example() -> Annotated[str, Path("file.txt")]:
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_task_without_path_that_return(runner, tmp_path, parallel_backend):
     source = """
     from pathlib import Path
@@ -264,7 +263,7 @@ def test_task_without_path_that_return(runner, tmp_path, parallel_backend):
 
 @pytest.mark.end_to_end()
 @pytest.mark.parametrize("flag", ["--pdb", "--trace", "--dry-run"])
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_parallel_execution_is_deactivated(runner, tmp_path, flag, parallel_backend):
     tmp_path.joinpath("task_example.py").write_text("def task_example(): pass")
     result = runner.invoke(
@@ -278,7 +277,7 @@ def test_parallel_execution_is_deactivated(runner, tmp_path, flag, parallel_back
 @pytest.mark.end_to_end()
 @pytest.mark.parametrize("code", ["breakpoint()", "import pdb; pdb.set_trace()"])
 @pytest.mark.parametrize(
-    "parallel_backend", [i for i in PARALLEL_BACKENDS if i != ParallelBackend.THREADS]
+    "parallel_backend", [i for i in ParallelBackend if i != ParallelBackend.THREADS]
 )
 def test_raise_error_on_breakpoint(runner, tmp_path, code, parallel_backend):
     tmp_path.joinpath("task_example.py").write_text(f"def task_example(): {code}")
@@ -290,7 +289,7 @@ def test_raise_error_on_breakpoint(runner, tmp_path, code, parallel_backend):
 
 
 @pytest.mark.end_to_end()
-@pytest.mark.parametrize("parallel_backend", PARALLEL_BACKENDS)
+@pytest.mark.parametrize("parallel_backend", ParallelBackend)
 def test_task_partialed(runner, tmp_path, parallel_backend):
     source = """
     from pathlib import Path