test_sys.py 文件源码

def test_intern(self):
        global numruns
        numruns += 1
        self.assertRaises(TypeError, sys.intern)
        s = "never interned before" + str(numruns)
        self.assertTrue(sys.intern(s) is s)
        s2 = s.swapcase().swapcase()
        self.assertTrue(sys.intern(s2) is s)

        # Subclasses of string can't be interned, because they
        # provide too much opportunity for insane things to happen.
        # We don't want them in the interned dict and if they aren't
        # actually interned, we don't want to create the appearance
        # that they are by allowing intern() to succeed.
        class S(str):
            def __hash__(self):
                return 123

        self.assertRaises(TypeError, sys.intern, S("abc"))