Python types.new_class() Examples

def test_prepare_class(self):
        # Basic test of metaclass derivation
        expected_ns = {}
        class A(type):
            def __new__(*args, **kwargs):
                return type.__new__(*args, **kwargs)

            def __prepare__(*args):
                return expected_ns

        B = types.new_class("B", (object,))
        C = types.new_class("C", (object,), {"metaclass": A})

        # The most derived metaclass of D is A rather than type.
        meta, ns, kwds = types.prepare_class("D", (B, C), {"metaclass": type})
        self.assertIs(meta, A)
        self.assertIs(ns, expected_ns)
        self.assertEqual(len(kwds), 0) 

def test_metaclass_override_function(self):
        # Special case: the given metaclass isn't a class,
        # so there is no metaclass calculation.
        class A(metaclass=self.Meta):
            pass

        marker = object()
        def func(*args, **kwargs):
            return marker

        X = types.new_class("X", (), {"metaclass": func})
        Y = types.new_class("Y", (object,), {"metaclass": func})
        Z = types.new_class("Z", (A,), {"metaclass": func})
        self.assertIs(marker, X)
        self.assertIs(marker, Y)
        self.assertIs(marker, Z) 

def patch_config_as_nothrow(instance):
    if "NoThrow" in [instance.__name__, instance.__class__.__name__]:
        return instance

    if type(instance) == type:
        instance = types.new_class(instance.__name__ + "NoThrow", (instance, ), dict(metaclass=NoThrowMeta))
        for (k, v) in inspect.getmembers(instance):
            if not k.startswith("__") and type(v) == type:
                type.__setattr__(instance, k, patch_config_as_nothrow(v))
    else:
        for (k, v) in inspect.getmembers(instance.__class__):
            if not k.startswith("__") and type(v) == type:
                type.__setattr__(instance.__class__, k, patch_config_as_nothrow(v))
        instance.__class__ = type(instance.__class__.__name__ + "NoThrow", (instance.__class__, NoThrowBase), {})

    return instance 

def specialize_class(cls, kind, base=None, **kwargs):
    # XXX Support passing in submodule names--load (and cache) them?
    # That would clean up the test modules a bit more.
    if base is None:
        base = unittest.TestCase
    elif not isinstance(base, type):
        base = base[kind]
    name = '{}_{}'.format(kind, cls.__name__)
    bases = (cls, base)
    specialized = types.new_class(name, bases)
    specialized.__module__ = cls.__module__
    specialized._NAME = cls.__name__
    specialized._KIND = kind
    for attr, values in kwargs.items():
        value = values[kind]
        setattr(specialized, attr, value)
    return specialized 

def test_metaclass_override_function(self):
        # Special case: the given metaclass isn't a class,
        # so there is no metaclass calculation.
        class A(metaclass=self.Meta):
            pass

        marker = object()
        def func(*args, **kwargs):
            return marker

        X = types.new_class("X", (), {"metaclass": func})
        Y = types.new_class("Y", (object,), {"metaclass": func})
        Z = types.new_class("Z", (A,), {"metaclass": func})
        self.assertIs(marker, X)
        self.assertIs(marker, Y)
        self.assertIs(marker, Z) 

def specialize_class(cls, kind, base=None, **kwargs):
    # XXX Support passing in submodule names--load (and cache) them?
    # That would clean up the test modules a bit more.
    if base is None:
        base = unittest.TestCase
    elif not isinstance(base, type):
        base = base[kind]
    name = '{}_{}'.format(kind, cls.__name__)
    bases = (cls, base)
    specialized = types.new_class(name, bases)
    specialized.__module__ = cls.__module__
    specialized._NAME = cls.__name__
    specialized._KIND = kind
    for attr, values in kwargs.items():
        value = values[kind]
        setattr(specialized, attr, value)
    return specialized 

def test_prepare_class(self):
        # Basic test of metaclass derivation
        expected_ns = {}
        class A(type):
            def __new__(*args, **kwargs):
                return type.__new__(*args, **kwargs)

            def __prepare__(*args):
                return expected_ns

        B = types.new_class("B", (object,))
        C = types.new_class("C", (object,), {"metaclass": A})

        # The most derived metaclass of D is A rather than type.
        meta, ns, kwds = types.prepare_class("D", (B, C), {"metaclass": type})
        self.assertIs(meta, A)
        self.assertIs(ns, expected_ns)
        self.assertEqual(len(kwds), 0) 

def test_metaclass_override_function(self):
        # Special case: the given metaclass isn't a class,
        # so there is no metaclass calculation.
        class A(metaclass=self.Meta):
            pass

        marker = object()
        def func(*args, **kwargs):
            return marker

        X = types.new_class("X", (), {"metaclass": func})
        Y = types.new_class("Y", (object,), {"metaclass": func})
        Z = types.new_class("Z", (A,), {"metaclass": func})
        self.assertIs(marker, X)
        self.assertIs(marker, Y)
        self.assertIs(marker, Z) 

def _make_skeleton_class(type_constructor, name, bases, type_kwargs,
                         class_tracker_id, extra):
    """Build dynamic class with an empty __dict__ to be filled once memoized

    If class_tracker_id is not None, try to lookup an existing class definition
    matching that id. If none is found, track a newly reconstructed class
    definition under that id so that other instances stemming from the same
    class id will also reuse this class definition.

    The "extra" variable is meant to be a dict (or None) that can be used for
    forward compatibility shall the need arise.
    """
    skeleton_class = types.new_class(
        name, bases, {'metaclass': type_constructor},
        lambda ns: ns.update(type_kwargs)
    )
    return _lookup_class_or_track(class_tracker_id, skeleton_class) 

def test_prepare_class(self):
        # Basic test of metaclass derivation
        expected_ns = {}
        class A(type):
            def __new__(*args, **kwargs):
                return type.__new__(*args, **kwargs)

            def __prepare__(*args):
                return expected_ns

        B = types.new_class("B", (object,))
        C = types.new_class("C", (object,), {"metaclass": A})

        # The most derived metaclass of D is A rather than type.
        meta, ns, kwds = types.prepare_class("D", (B, C), {"metaclass": type})
        self.assertIs(meta, A)
        self.assertIs(ns, expected_ns)
        self.assertEqual(len(kwds), 0) 

def test_prepare_class(self):
        # Basic test of metaclass derivation
        expected_ns = {}
        class A(type):
            def __new__(*args, **kwargs):
                return type.__new__(*args, **kwargs)

            def __prepare__(*args):
                return expected_ns

        B = types.new_class("B", (object,))
        C = types.new_class("C", (object,), {"metaclass": A})

        # The most derived metaclass of D is A rather than type.
        meta, ns, kwds = types.prepare_class("D", (B, C), {"metaclass": type})
        self.assertIs(meta, A)
        self.assertIs(ns, expected_ns)
        self.assertEqual(len(kwds), 0) 

def test_metaclass_override_function(self):
        # Special case: the given metaclass isn't a class,
        # so there is no metaclass calculation.
        class A(metaclass=self.Meta):
            pass

        marker = object()
        def func(*args, **kwargs):
            return marker

        X = types.new_class("X", (), {"metaclass": func})
        Y = types.new_class("Y", (object,), {"metaclass": func})
        Z = types.new_class("Z", (A,), {"metaclass": func})
        self.assertIs(marker, X)
        self.assertIs(marker, Y)
        self.assertIs(marker, Z) 

def patch_config_as_nothrow(instance):
    if "NoThrow" in [instance.__name__, instance.__class__.__name__]:
        return instance

    if type(instance) == type:
        instance = types.new_class(instance.__name__ + "NoThrow", (instance, ), dict(metaclass=NoThrowMeta))
        for (k, v) in inspect.getmembers(instance):
            if not k.startswith("__") and type(v) == type:
                type.__setattr__(instance, k, patch_config_as_nothrow(v))
    else:
        for (k, v) in inspect.getmembers(instance.__class__):
            if not k.startswith("__") and type(v) == type:
                type.__setattr__(instance.__class__, k, patch_config_as_nothrow(v))
        instance.__class__ = type(instance.__class__.__name__ + "NoThrow", (instance.__class__, NoThrowBase), {})

    return instance 

def mk_bitstruct( cls_name, fields, *, namespace=None, add_init=True,
                   add_str=True, add_repr=True, add_hash=True ):

  # copy namespace since  will mutate it
  namespace = {} if namespace is None else namespace.copy()

  # We assume fields is a dictionary and thus there won't be duplicate
  # field names. So we only check if the field names are indeed strings
  # and that they are not keywords.
  annos = {}
  for name, f in fields.items():
    if not isinstance( name, str ) or not name.isidentifier():
      raise TypeError( f'Field name {name!r} is not a valid identifier!' )
    if keyword.iskeyword( name ):
      raise TypeError( f'Field name {name!r} is a keyword!' )
    annos[ name ] = f

  namespace['__annotations__'] = annos
  cls = types.new_class( cls_name, (), {}, lambda ns: ns.update( namespace ) )
  return bitstruct( cls, add_init=add_init, add_str=add_str,
                    add_repr=add_repr, add_hash=add_hash ) 

def _new_nonterm(self, clsname, clsdict=None, clskwds=None,
                     clsbases=(Nonterm,)):
        if clsdict is None:
            clsdict = {}
        if clskwds is None:
            clskwds = {}
        mod = sys.modules[self.name]

        def clsexec(ns):
            ns['__module__'] = self.name
            for k, v in clsdict.items():
                ns[k] = v
            return ns

        cls = types.new_class(clsname, clsbases, clskwds, clsexec)
        setattr(mod, clsname, cls)
        return cls 

def conlist(item_type: Type[T], *, min_items: int = None, max_items: int = None) -> Type[List[T]]:
    # __args__ is needed to conform to typing generics api
    namespace = {'min_items': min_items, 'max_items': max_items, 'item_type': item_type, '__args__': [item_type]}
    # We use new_class to be able to deal with Generic types
    return new_class('ConstrainedListValue', (ConstrainedList,), {}, lambda ns: ns.update(namespace))


# This types superclass should be Set[T], but cython chokes on that... 

def test_new_class_exec_body(self):
        Meta = self.Meta
        def func(ns):
            ns["x"] = 0
        C = types.new_class("C", (), {"metaclass": Meta, "z": 2}, func)
        self.assertIsInstance(C, Meta)
        self.assertEqual(C.x, 0)
        self.assertEqual(C.y, 1)
        self.assertEqual(C.z, 2) 

def test_tests_fail_1(self):
        SimpleTestCase = types.new_class('SimpleTestCase',
                                         (BaseSimpleTestCase, tb.TestCase))

        suite = unittest.TestSuite()
        suite.addTest(SimpleTestCase('test_tests_zero_error'))

        result = unittest.TestResult()
        suite.run(result)

        self.assertIn('ZeroDivisionError', result.errors[0][1]) 

def test_new_class_metaclass_keywords(self):
        #Test that keywords are passed to the metaclass:
        def meta_func(name, bases, ns, **kw):
            return name, bases, ns, kw
        res = types.new_class("X",
                              (int, object),
                              dict(metaclass=meta_func, x=0))
        self.assertEqual(res, ("X", (int, object), {}, {"x": 0})) 

def test_new_class_exec_body(self):
        Meta = self.Meta
        def func(ns):
            ns["x"] = 0
        C = types.new_class("C", (), {"metaclass": Meta, "z": 2}, func)
        self.assertIsInstance(C, Meta)
        self.assertEqual(C.x, 0)
        self.assertEqual(C.y, 1)
        self.assertEqual(C.z, 2) 

def conset(item_type: Type[T], *, min_items: int = None, max_items: int = None) -> Type[Set[T]]:
    # __args__ is needed to conform to typing generics api
    namespace = {'min_items': min_items, 'max_items': max_items, 'item_type': item_type, '__args__': [item_type]}
    # We use new_class to be able to deal with Generic types
    return new_class('ConstrainedSetValue', (ConstrainedSet,), {}, lambda ns: ns.update(namespace)) 

def test_new_class_basics(self):
        C = types.new_class("C")
        self.assertEqual(C.__name__, "C")
        self.assertEqual(C.__bases__, (object,)) 

def test_new_class_subclass(self):
        C = types.new_class("C", (int,))
        self.assertTrue(issubclass(C, int)) 

def test_new_class_meta(self):
        Meta = self.Meta
        settings = {"metaclass": Meta, "z": 2}
        # We do this twice to make sure the passed in dict isn't mutated
        for i in range(2):
            C = types.new_class("C" + str(i), (), settings)
            self.assertIsInstance(C, Meta)
            self.assertEqual(C.y, 1)
            self.assertEqual(C.z, 2) 

def interface_as_type(typ, module):
    # type: (Interface, str) -> type
    # we don't add the fields yet -- these types may not exist yet.
    return new_class(
        str(typ.name),
        (types.Namespace,),
        kwds={"metaclass": types.Interface},
        exec_body=methodcaller(
            "update",
            {"__doc__": typ.desc, "__raw__": typ, "__module__": module},
        ),
    ) 

def test_new_class_metaclass_keywords(self):
        #Test that keywords are passed to the metaclass:
        def meta_func(name, bases, ns, **kw):
            return name, bases, ns, kw
        res = types.new_class("X",
                              (int, object),
                              dict(metaclass=meta_func, x=0))
        self.assertEqual(res, ("X", (int, object), {}, {"x": 0})) 

def test_new_class_meta_with_base(self):
        Meta = self.Meta
        def func(ns):
            ns["x"] = 0
        C = types.new_class(name="C",
                            bases=(int,),
                            kwds=dict(metaclass=Meta, z=2),
                            exec_body=func)
        self.assertTrue(issubclass(C, int))
        self.assertIsInstance(C, Meta)
        self.assertEqual(C.x, 0)
        self.assertEqual(C.y, 1)
        self.assertEqual(C.z, 2) 

def test_new_class_with_mro_entry(self):
        class A: pass
        class C:
            def __mro_entries__(self, bases):
                return (A,)
        c = C()
        D = types.new_class('D', (c,), {})
        self.assertEqual(D.__bases__, (A,))
        self.assertEqual(D.__orig_bases__, (c,))
        self.assertEqual(D.__mro__, (D, A, object)) 

def test_new_class_with_mro_entry_none(self):
        class A: pass
        class B: pass
        class C:
            def __mro_entries__(self, bases):
                return ()
        c = C()
        D = types.new_class('D', (A, c, B), {})
        self.assertEqual(D.__bases__, (A, B))
        self.assertEqual(D.__orig_bases__, (A, c, B))
        self.assertEqual(D.__mro__, (D, A, B, object)) 

def test_new_class_with_mro_entry_error(self):
        class A: pass
        class C:
            def __mro_entries__(self, bases):
                return A
        c = C()
        with self.assertRaises(TypeError):
            types.new_class('D', (c,), {})