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