bpo-32596: Lazy import concurrent.futures.process and thread (GH-5241)
diff --git a/Lib/concurrent/futures/__init__.py b/Lib/concurrent/futures/__init__.py
index ba8de16..72aca81 100644
--- a/Lib/concurrent/futures/__init__.py
+++ b/Lib/concurrent/futures/__init__.py
@@ -15,5 +15,36 @@
Executor,
wait,
as_completed)
-from concurrent.futures.process import ProcessPoolExecutor
-from concurrent.futures.thread import ThreadPoolExecutor
+
+__all__ = (
+ 'FIRST_COMPLETED',
+ 'FIRST_EXCEPTION',
+ 'ALL_COMPLETED',
+ 'CancelledError',
+ 'TimeoutError',
+ 'BrokenExecutor',
+ 'Future',
+ 'Executor',
+ 'wait',
+ 'as_completed',
+ 'ProcessPoolExecutor',
+ 'ThreadPoolExecutor',
+)
+
+
+def __dir__():
+ return __all__ + ('__author__', '__doc__')
+
+
+def __getattr__(name):
+ global ProcessPoolExecutor, ThreadPoolExecutor
+
+ if name == 'ProcessPoolExecutor':
+ from .process import ProcessPoolExecutor
+ return ProcessPoolExecutor
+
+ if name == 'ThreadPoolExecutor':
+ from .thread import ThreadPoolExecutor
+ return ThreadPoolExecutor
+
+ raise AttributeError(f"module {__name__} has no attribute {name}")
diff --git a/Misc/NEWS.d/next/Library/2018-01-19-19-57-45.bpo-32596.4aVIie.rst b/Misc/NEWS.d/next/Library/2018-01-19-19-57-45.bpo-32596.4aVIie.rst
new file mode 100644
index 0000000..a90f7d1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-01-19-19-57-45.bpo-32596.4aVIie.rst
@@ -0,0 +1,4 @@
+``concurrent.futures`` imports ``ThreadPoolExecutor`` and
+``ProcessPoolExecutor`` lazily (using :pep:`562`).
+It makes ``import asyncio`` about 15% faster because asyncio
+uses only ``ThreadPoolExecutor`` by default.