test_descr.py 文件源码

def test_altmro(self):
        # Testing mro() and overriding it...
        class A(object):
            def f(self): return "A"
        class B(A):
            pass
        class C(A):
            def f(self): return "C"
        class D(B, C):
            pass
        self.assertEqual(D.mro(), [D, B, C, A, object])
        self.assertEqual(D.__mro__, (D, B, C, A, object))
        self.assertEqual(D().f(), "C")

        class PerverseMetaType(type):
            def mro(cls):
                L = type.mro(cls)
                L.reverse()
                return L
        class X(D,B,C,A):
            __metaclass__ = PerverseMetaType
        self.assertEqual(X.__mro__, (object, A, C, B, D, X))
        self.assertEqual(X().f(), "A")

        try:
            class X(object):
                class __metaclass__(type):
                    def mro(self):
                        return [self, dict, object]
            # In CPython, the class creation above already raises
            # TypeError, as a protection against the fact that
            # instances of X would segfault it.  In other Python
            # implementations it would be ok to let the class X
            # be created, but instead get a clean TypeError on the
            # __setitem__ below.
            x = object.__new__(X)
            x[5] = 6
        except TypeError:
            pass
        else:
            self.fail("devious mro() return not caught")

        try:
            class X(object):
                class __metaclass__(type):
                    def mro(self):
                        return [1]
        except TypeError:
            pass
        else:
            self.fail("non-class mro() return not caught")

        try:
            class X(object):
                class __metaclass__(type):
                    def mro(self):
                        return 1
        except TypeError:
            pass
        else:
            self.fail("non-sequence mro() return not caught")