Fix behavior to follow test_free_reference requirements (generator ho…

…lds no reference to result at the moment it yields Reduce line lengths to PEP8 limits
python · MojoVampire · Mar 18, 2017 · May 6, 2019 · May 6, 2019 · May 6, 2019
commit 3c38fabdfe9d625064625b4fb84aa41d59bf250d
diff --git a/Lib/concurrent/futures/_base.py b/Lib/concurrent/futures/_base.py
@@ -601,8 +601,9 @@ def map(self, fn, *iterables, timeout=None, chunksize=1, prefetch=None):
             raise ValueError("prefetch count may not be negative")
 
         argsiter = zip(*iterables)
+        initialargs = itertools.islice(argsiter, self._max_workers + prefetch)
 
-        fs = collections.deque(self.submit(fn, *args) for args in itertools.islice(argsiter, self._max_workers + prefetch))
+        fs = collections.deque(self.submit(fn, *args) for args in initialargs)
 
         # Yield must be hidden in closure so that the futures are submitted
         # before the first iterator value is required.
@@ -611,9 +612,9 @@ def result_iterator():
             try:
                 while fs:
                     if timeout is None:
-                        res = fs[0].result()
+                        res = [fs[0].result()]
                     else:
-                        res = fs[0].result(end_time - time.monotonic())
+                        res = [fs[0].result(end_time - time.monotonic())]
 
                     # Got a result, future needn't be cancelled
                     del fs[0]
@@ -628,7 +629,7 @@ def result_iterator():
                         else:
                             fs.append(self.submit(fn, *args))
 
-                    yield res
+                    yield res.pop()
             finally:
                 for future in fs:
                     future.cancel()