Showing content from http://svn.python.org/projects/python/branches/tk_and_idle_maintenance/Lib/test/test_typechecks.py below:
"""Unit tests for __instancecheck__ and __subclasscheck__.""" import unittest from test import test_support class ABC(type): def __instancecheck__(cls, inst): """Implement isinstance(inst, cls).""" return any(cls.__subclasscheck__(c) for c in set([type(inst), inst.__class__])) def __subclasscheck__(cls, sub): """Implement issubclass(sub, cls).""" candidates = cls.__dict__.get("__subclass__", set()) | set([cls]) return any(c in candidates for c in sub.mro()) class Integer: __metaclass__ = ABC __subclass__ = set([int]) class SubInt(Integer): pass class TypeChecksTest(unittest.TestCase): def testIsSubclassInternal(self): self.assertEqual(Integer.__subclasscheck__(int), True) self.assertEqual(Integer.__subclasscheck__(float), False) def testIsSubclassBuiltin(self): self.assertEqual(issubclass(int, Integer), True) self.assertEqual(issubclass(int, (Integer,)), True) self.assertEqual(issubclass(float, Integer), False) self.assertEqual(issubclass(float, (Integer,)), False) def testIsInstanceBuiltin(self): self.assertEqual(isinstance(42, Integer), True) self.assertEqual(isinstance(42, (Integer,)), True) self.assertEqual(isinstance(3.14, Integer), False) self.assertEqual(isinstance(3.14, (Integer,)), False) def testIsInstanceActual(self): self.assertEqual(isinstance(Integer(), Integer), True) self.assertEqual(isinstance(Integer(), (Integer,)), True) def testIsSubclassActual(self): self.assertEqual(issubclass(Integer, Integer), True) self.assertEqual(issubclass(Integer, (Integer,)), True) def testSubclassBehavior(self): self.assertEqual(issubclass(SubInt, Integer), True) self.assertEqual(issubclass(SubInt, (Integer,)), True) self.assertEqual(issubclass(SubInt, SubInt), True) self.assertEqual(issubclass(SubInt, (SubInt,)), True) self.assertEqual(issubclass(Integer, SubInt), False) self.assertEqual(issubclass(Integer, (SubInt,)), False) self.assertEqual(issubclass(int, SubInt), False) self.assertEqual(issubclass(int, (SubInt,)), False) self.assertEqual(isinstance(SubInt(), Integer), True) self.assertEqual(isinstance(SubInt(), (Integer,)), True) self.assertEqual(isinstance(SubInt(), SubInt), True) self.assertEqual(isinstance(SubInt(), (SubInt,)), True) self.assertEqual(isinstance(42, SubInt), False) self.assertEqual(isinstance(42, (SubInt,)), False) def test_oldstyle(self): # These should just be ignored. class X: def __instancecheck__(self, inst): return True def __subclasscheck__(self, cls): return True class Sub(X): pass self.assertFalse(isinstance(3, X)) self.assertTrue(isinstance(X(), X)) self.assertFalse(issubclass(int, X)) self.assertTrue(issubclass(Sub, X)) def test_main(): test_support.run_unittest(TypeChecksTest) if __name__ == "__main__": unittest.main()
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