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-rw-r--r--Lib/multiprocessing/pool.py1
-rw-r--r--Lib/test/test_multiprocessing.py18
2 files changed, 16 insertions, 3 deletions
diff --git a/Lib/multiprocessing/pool.py b/Lib/multiprocessing/pool.py
index 0c29e644ff..ccee9612d4 100644
--- a/Lib/multiprocessing/pool.py
+++ b/Lib/multiprocessing/pool.py
@@ -584,6 +584,7 @@ class MapResult(ApplyResult):
if chunksize <= 0:
self._number_left = 0
self._ready = True
+ del cache[self._job]
else:
self._number_left = length//chunksize + bool(length % chunksize)
diff --git a/Lib/test/test_multiprocessing.py b/Lib/test/test_multiprocessing.py
index 5f1bba32a2..0d98a1498c 100644
--- a/Lib/test/test_multiprocessing.py
+++ b/Lib/test/test_multiprocessing.py
@@ -1178,6 +1178,18 @@ class _TestPool(BaseTestCase):
join()
self.assertLess(join.elapsed, 0.5)
+ def test_empty_iterable(self):
+ # See Issue 12157
+ p = self.Pool(1)
+
+ self.assertEqual(p.map(sqr, []), [])
+ self.assertEqual(list(p.imap(sqr, [])), [])
+ self.assertEqual(list(p.imap_unordered(sqr, [])), [])
+ self.assertEqual(p.map_async(sqr, []).get(), [])
+
+ p.close()
+ p.join()
+
def raising():
raise KeyError("key")
@@ -2176,7 +2188,7 @@ class ProcessesMixin(object):
'Queue', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore',
'Condition', 'Event', 'Value', 'Array', 'RawValue',
'RawArray', 'current_process', 'active_children', 'Pipe',
- 'connection', 'JoinableQueue'
+ 'connection', 'JoinableQueue', 'Pool'
)))
testcases_processes = create_test_cases(ProcessesMixin, type='processes')
@@ -2190,7 +2202,7 @@ class ManagerMixin(object):
locals().update(get_attributes(manager, (
'Queue', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore',
'Condition', 'Event', 'Value', 'Array', 'list', 'dict',
- 'Namespace', 'JoinableQueue'
+ 'Namespace', 'JoinableQueue', 'Pool'
)))
testcases_manager = create_test_cases(ManagerMixin, type='manager')
@@ -2204,7 +2216,7 @@ class ThreadsMixin(object):
'Queue', 'Lock', 'RLock', 'Semaphore', 'BoundedSemaphore',
'Condition', 'Event', 'Value', 'Array', 'current_process',
'active_children', 'Pipe', 'connection', 'dict', 'list',
- 'Namespace', 'JoinableQueue'
+ 'Namespace', 'JoinableQueue', 'Pool'
)))
testcases_threads = create_test_cases(ThreadsMixin, type='threads')