comment on weakref

Author: ebonnal

Lib/concurrent/futures/_base.py

@@ -614,6 +614,8 @@ def map(self, fn, *iterables, timeout=None, chunksize=1, buffersize=None):
         else:
             fs = [self.submit(fn, *args) for args in args_iter]
 
+        # use a weak reference to ensure that the executor can be garbage
+        # collected independently of the result_iterator closure.
         executor_weakref = weakref.ref(self)
 
         # Yield must be hidden in closure so that the futures are submitted