bpo-35477: multiprocessing.Pool.__enter__() fails if called twice (GH-11134)
multiprocessing.Pool.__enter__() now fails if the pool is not
running: "with pool:" fails if used more than once.
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index 2b3cc59..c077541 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -261,6 +261,10 @@
self._quick_put = self._inqueue._writer.send
self._quick_get = self._outqueue._reader.recv
+ def _check_running(self):
+ if self._state != RUN:
+ raise ValueError("Pool not running")
+
def apply(self, func, args=(), kwds={}):
'''
Equivalent of `func(*args, **kwds)`.
@@ -306,8 +310,7 @@
'''
Equivalent of `map()` -- can be MUCH slower than `Pool.map()`.
'''
- if self._state != RUN:
- raise ValueError("Pool not running")
+ self._check_running()
if chunksize == 1:
result = IMapIterator(self._cache)
self._taskqueue.put(
@@ -336,8 +339,7 @@
'''
Like `imap()` method but ordering of results is arbitrary.
'''
- if self._state != RUN:
- raise ValueError("Pool not running")
+ self._check_running()
if chunksize == 1:
result = IMapUnorderedIterator(self._cache)
self._taskqueue.put(
@@ -366,8 +368,7 @@
'''
Asynchronous version of `apply()` method.
'''
- if self._state != RUN:
- raise ValueError("Pool not running")
+ self._check_running()
result = ApplyResult(self._cache, callback, error_callback)
self._taskqueue.put(([(result._job, 0, func, args, kwds)], None))
return result
@@ -385,8 +386,7 @@
'''
Helper function to implement map, starmap and their async counterparts.
'''
- if self._state != RUN:
- raise ValueError("Pool not running")
+ self._check_running()
if not hasattr(iterable, '__len__'):
iterable = list(iterable)
@@ -625,6 +625,7 @@
p.join()
def __enter__(self):
+ self._check_running()
return self
def __exit__(self, exc_type, exc_val, exc_tb):
diff --git a/Lib/test/_test_multiprocessing.py b/Lib/test/_test_multiprocessing.py
index 0b0fe7c..a2dc53c 100644
--- a/Lib/test/_test_multiprocessing.py
+++ b/Lib/test/_test_multiprocessing.py
@@ -2561,6 +2561,22 @@
# they were released too.
self.assertEqual(CountedObject.n_instances, 0)
+ def test_enter(self):
+ if self.TYPE == 'manager':
+ self.skipTest("test not applicable to manager")
+
+ pool = self.Pool(1)
+ with pool:
+ pass
+ # call pool.terminate()
+ # pool is no longer running
+
+ with self.assertRaises(ValueError):
+ # bpo-35477: pool.__enter__() fails if the pool is not running
+ with pool:
+ pass
+ pool.join()
+
def raising():
raise KeyError("key")
diff --git a/Misc/NEWS.d/next/Library/2018-12-13-00-10-51.bpo-35477.hHyy06.rst b/Misc/NEWS.d/next/Library/2018-12-13-00-10-51.bpo-35477.hHyy06.rst
new file mode 100644
index 0000000..524df71
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-12-13-00-10-51.bpo-35477.hHyy06.rst
@@ -0,0 +1,2 @@
+:meth:`multiprocessing.Pool.__enter__` now fails if the pool is not running:
+``with pool:`` fails if used more than once.