make inspect.isabstract() always return a boolean; add a test for it, too #7069

Lib/inspect.py

@@ -242,7 +242,7 @@ def isroutine(object):
 
 def isabstract(object):
     """Return true if the object is an abstract base class (ABC)."""
-    return isinstance(object, type) and object.__flags__ & TPFLAGS_IS_ABSTRACT
+    return bool(isinstance(object, type) and object.__flags__ & TPFLAGS_IS_ABSTRACT)
 
 def getmembers(object, predicate=None):
     """Return all members of an object as (name, value) pairs sorted by name.

Lib/test/test_inspect.py

@@ -115,6 +115,29 @@ class TestPredicates(IsTestBase):
         self.assertTrue('a' in members)
         self.assertTrue('b' not in members)
 
+    def test_isabstract(self):
+        from abc import ABCMeta, abstractmethod
+
+        class AbstractClassExample(object):
+            __metaclass__ = ABCMeta
+
+            @abstractmethod
+            def foo(self):
+                pass
+
+        class ClassExample(AbstractClassExample):
+            def foo(self):
+                pass
+
+        a = ClassExample()
+
+        # Test general behaviour.
+        self.assertTrue(inspect.isabstract(AbstractClassExample))
+        self.assertFalse(inspect.isabstract(ClassExample))
+        self.assertFalse(inspect.isabstract(a))
+        self.assertFalse(inspect.isabstract(int))
+        self.assertFalse(inspect.isabstract(5))
+
 
 class TestInterpreterStack(IsTestBase):
     def __init__(self, *args, **kwargs):

Misc/NEWS

@@ -405,6 +405,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #7069: Make inspect.isabstract() return a boolean.
+
 - Add support to the `ihooks` module for relative imports.
 
 - Issue #6894: Fixed the issue urllib2 doesn't respect "no_proxy" environment