Enum: make Flag and IntFlag members iterable (GH-22221)

Author: ethanfurman

Doc/library/enum.rst

@@ -656,6 +656,13 @@ be combined with them::
     >>> Perm.X | 8
     <Perm.8|X: 9>
 
+:class:`IntFlag` members can also be iterated over::
+
+    >>> list(RW)
+    [<Perm.R: 4>, <Perm.W: 2>]
+
+.. versionadded:: 3.10
+
 
 Flag
 ^^^^
@@ -709,6 +716,14 @@ value::
     >>> bool(Color.BLACK)
     False
 
+:class:`Flag` members can also be iterated over::
+
+    >>> purple = Color.RED | Color.BLUE
+    >>> list(purple)
+    [<Color.BLUE: 2>, <Color.RED: 1>]
+
+.. versionadded:: 3.10
+
 .. note::
 
     For the majority of new code, :class:`Enum` and :class:`Flag` are strongly

Lib/enum.py

@@ -753,6 +753,10 @@ def __contains__(self, other):
                     type(other).__qualname__, self.__class__.__qualname__))
         return other._value_ & self._value_ == other._value_
 
+    def __iter__(self):
+        members, extra_flags = _decompose(self.__class__, self.value)
+        return (m for m in members if m._value_ != 0)
+
     def __repr__(self):
         cls = self.__class__
         if self._name_ is not None:

Lib/test/test_enum.py

@@ -2350,6 +2350,12 @@ def test_member_contains(self):
         self.assertFalse(W in RX)
         self.assertFalse(X in RW)
 
+    def test_member_iter(self):
+        Color = self.Color
+        self.assertEqual(list(Color.PURPLE), [Color.BLUE, Color.RED])
+        self.assertEqual(list(Color.BLUE), [Color.BLUE])
+        self.assertEqual(list(Color.GREEN), [Color.GREEN])
+
     def test_auto_number(self):
         class Color(Flag):
             red = auto()
@@ -2805,6 +2811,12 @@ def test_member_contains(self):
         with self.assertRaises(TypeError):
             self.assertFalse('test' in RW)
 
+    def test_member_iter(self):
+        Color = self.Color
+        self.assertEqual(list(Color.PURPLE), [Color.BLUE, Color.RED])
+        self.assertEqual(list(Color.BLUE), [Color.BLUE])
+        self.assertEqual(list(Color.GREEN), [Color.GREEN])
+
     def test_bool(self):
         Perm = self.Perm
         for f in Perm:

Misc/NEWS.d/next/Library/2020-09-12-16-18-42.bpo-32218.IpYkEe.rst

@@ -0,0 +1 @@
+`enum.Flag` and `enum.IntFlag` members are now iterable