From f007876bd64def2829a242e0cf5adfd3ef25c4be Mon Sep 17 00:00:00 2001 From: Brian Quinlan Date: Fri, 8 Apr 2011 08:19:33 +1000 Subject: [PATCH] Issue #11777: Executor.map does not submit futures until iter.next() is called --- Lib/concurrent/futures/_base.py | 22 +++++++++++++--------- Lib/test/test_concurrent_futures.py | 10 +++++++++- 2 files changed, 22 insertions(+), 10 deletions(-) diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py index 79b91d495fc..6cfded30755 100644 --- a/Lib/concurrent/futures/_base.py +++ b/Lib/concurrent/futures/_base.py @@ -536,15 +536,19 @@ class Executor(object): fs = [self.submit(fn, *args) for args in zip(*iterables)] - try: - for future in fs: - if timeout is None: - yield future.result() - else: - yield future.result(end_time - time.time()) - finally: - for future in fs: - future.cancel() + # Yield must be hidden in closure so that the futures are submitted + # before the first iterator value is required. + def result_iterator(): + try: + for future in fs: + if timeout is None: + yield future.result() + else: + yield future.result(end_time - time.time()) + finally: + for future in fs: + future.cancel() + return result_iterator() def shutdown(self, wait=True): """Clean-up the resources associated with the Executor. diff --git a/Lib/test/test_concurrent_futures.py b/Lib/test/test_concurrent_futures.py index 2662af76cff..ec84a663079 100644 --- a/Lib/test/test_concurrent_futures.py +++ b/Lib/test/test_concurrent_futures.py @@ -369,7 +369,15 @@ class ExecutorTest(unittest.TestCase): class ThreadPoolExecutorTest(ThreadPoolMixin, ExecutorTest): - pass + def test_map_submits_without_iteration(self): + """Tests verifying issue 11777.""" + finished = [] + def record_finished(n): + finished.append(n) + + self.executor.map(record_finished, range(10)) + self.executor.shutdown(wait=True) + self.assertCountEqual(finished, range(10)) class ProcessPoolExecutorTest(ProcessPoolMixin, ExecutorTest):