diff --git a/Lib/collections/__init__.py b/Lib/collections/__init__.py
index 58607874be93d6..46849b0985d4d4 100644
--- a/Lib/collections/__init__.py
+++ b/Lib/collections/__init__.py
@@ -32,6 +32,7 @@
 from itertools import chain as _chain
 from itertools import repeat as _repeat
 from itertools import starmap as _starmap
+from itertools import islice as _islice
 from keyword import iskeyword as _iskeyword
 from operator import eq as _eq
 from operator import itemgetter as _itemgetter
@@ -1010,9 +1011,8 @@ def __len__(self):
         return len(set().union(*self.maps))     # reuses stored hash values if possible
 
     def __iter__(self):
-        d = {}
-        for mapping in reversed(self.maps):
-            d.update(dict.fromkeys(mapping))    # reuses stored hash values if possible
+        lazy_views = (key_view.keys() for key_view in reversed(self.maps))
+        d = dict.fromkeys(_chain.from_iterable(lazy_views))
         return iter(d)
 
     def __contains__(self, key):
@@ -1032,7 +1032,7 @@ def fromkeys(cls, iterable, *args):
 
     def copy(self):
         'New ChainMap or subclass with a new copy of maps[0] and refs to maps[1:]'
-        return self.__class__(self.maps[0].copy(), *self.maps[1:])
+        return self.__class__(self.maps[0].copy(), *_islice(self.maps, 1, None))
 
     __copy__ = copy
 
@@ -1050,7 +1050,7 @@ def new_child(self, m=None, **kwargs):      # like Django's Context.push()
     @property
     def parents(self):                          # like Django's Context.pop()
         'New ChainMap from maps[1:].'
-        return self.__class__(*self.maps[1:])
+        return self.__class__(*_islice(self.maps, 1, None))
 
     def __setitem__(self, key, value):
         self.maps[0][key] = value