bpo-30346: An iterator produced by the itertools.groupby() iterator (#1569)

now becames exhausted after advancing the groupby iterator.

1 files changed, 4 insertions, 3 deletions

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index c989e46..530c29d 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -401,13 +401,14 @@ loops that truncate the stream.
           def __iter__(self):
               return self
           def __next__(self):
+              self.id = object()
               while self.currkey == self.tgtkey:
                   self.currvalue = next(self.it)    # Exit on StopIteration
                   self.currkey = self.keyfunc(self.currvalue)
               self.tgtkey = self.currkey
-              return (self.currkey, self._grouper(self.tgtkey))
-          def _grouper(self, tgtkey):
-              while self.currkey == tgtkey:
+              return (self.currkey, self._grouper(self.tgtkey, self.id))
+          def _grouper(self, tgtkey, id):
+              while self.id is id and self.currkey == tgtkey:
                   yield self.currvalue
                   try:
                       self.currvalue = next(self.it)