Python typing.Protocol() Examples

def add_style_filter(self, style_filter: StyleFilterFunc) -> None:
        """Add a style filter function.

        Args:
            style_filter:
                A function for filtering table cells, the function required to implement
                the following Protocol:

                .. code-block:: python

                    class StyleFilterFunc(Protocol):
                        def __call__(self, cell: Cell, **kwargs: Any) -> Optional[Style]:
                            ...
        """

        self._style_filters.insert(0, style_filter) 

def _get_protocol_attrs(cls):
    attrs = set()
    for base in cls.__mro__[:-1]:  # without object
        if base.__name__ in ('Protocol', 'Generic'):
            continue
        annotations = getattr(base, '__annotations__', {})
        for attr in list(base.__dict__.keys()) + list(annotations.keys()):
            if (not attr.startswith('_abc_') and attr not in (
                    '__abstractmethods__', '__annotations__', '__weakref__',
                    '_is_protocol', '_is_runtime_protocol', '__dict__',
                    '__args__', '__slots__',
                    '__next_in_mro__', '__parameters__', '__origin__',
                    '__orig_bases__', '__extra__', '__tree_hash__',
                    '__doc__', '__subclasshook__', '__init__', '__new__',
                    '__module__', '_MutableMapping__marker', '_gorg')):
                attrs.add(attr)
    return attrs 

def __class_getitem__(cls, params):
            if not isinstance(params, tuple):
                params = (params,)
            if not params and cls is not Tuple:
                raise TypeError(
                    "Parameter list to {}[...] cannot be empty".format(cls.__qualname__))
            msg = "Parameters to generic types must be types."
            params = tuple(_type_check(p, msg) for p in params)
            if cls is Protocol:
                # Generic can only be subscripted with unique type variables.
                if not all(isinstance(p, TypeVar) for p in params):
                    i = 0
                    while isinstance(params[i], TypeVar):
                        i += 1
                    raise TypeError(
                        "Parameters to Protocol[...] must all be type variables."
                        " Parameter {} is {}".format(i + 1, params[i]))
                if len(set(params)) != len(params):
                    raise TypeError(
                        "Parameters to Protocol[...] must all be unique")
            else:
                # Subscripting a regular Generic subclass.
                _check_generic(cls, params)
            return _GenericAlias(cls, params) 

def test_typing_guard_for_protocol(self):
        self.flakes("""
            from typing import TYPE_CHECKING

            if TYPE_CHECKING:
                from typing import Protocol
            else:
                Protocol = object

            class C(Protocol):
                def f():  # type: () -> int
                    pass
        """) 

def test_new_repr_bare(self):
        T = TypeVar('T')
        self.assertEqual(repr(Generic[T]), 'typing.Generic[~T]')
        self.assertEqual(repr(typing._Protocol[T]), 'typing.Protocol[~T]')
        class C(typing.Dict[Any, Any]): ...
        # this line should just work
        repr(C.__mro__) 

def check(self, value, namespace):
        # return isinstance(value, self._cls)  # does not work for tg.Protocol
        return issubclass(type(value), self._cls)

# Note: 'typing'-module checkers must register _before_ this one: 

def __getitem__(self, params):
                # We also need to copy this from GenericMeta.__getitem__ to get
                # special treatment of "Protocol". (Comments removed for brevity.)
                if not isinstance(params, tuple):
                    params = (params,)
                if not params and _gorg(self) is not Tuple:
                    raise TypeError(
                        "Parameter list to %s[...] cannot be empty" % self.__qualname__)
                msg = "Parameters to generic types must be types."
                params = tuple(_type_check(p, msg) for p in params)
                if self in (Generic, Protocol):
                    if not all(isinstance(p, TypeVar) for p in params):
                        raise TypeError(
                            "Parameters to %r[...] must all be type variables" % self)
                    if len(set(params)) != len(params):
                        raise TypeError(
                            "Parameters to %r[...] must all be unique" % self)
                    tvars = params
                    args = params
                elif self in (Tuple, Callable):
                    tvars = _type_vars(params)
                    args = params
                elif self.__origin__ in (Generic, Protocol):
                    raise TypeError("Cannot subscript already-subscripted %s" %
                                    repr(self))
                else:
                    _check_generic(self, params)
                    tvars = _type_vars(params)
                    args = params

                prepend = (self,) if self.__origin__ is None else ()
                return self.__class__(self.__name__,
                                      prepend + self.__bases__,
                                      _no_slots_copy(self.__dict__),
                                      tvars=tvars,
                                      args=args,
                                      origin=self,
                                      extra=self.__extra__,
                                      orig_bases=self.__orig_bases__) 

def __new__(cls, *args, **kwds):
            if _gorg(cls) is Protocol:
                raise TypeError("Type Protocol cannot be instantiated; "
                                "it can be used only as a base class")
            if OLD_GENERICS:
                return _generic_new(_next_in_mro(cls), cls, *args, **kwds)
            return _generic_new(cls.__next_in_mro__, cls, *args, **kwds) 

def __init__(cls, *args, **kwargs):
            super().__init__(*args, **kwargs)
            if not cls.__dict__.get('_is_protocol', None):
                cls._is_protocol = any(b is Protocol or
                                       isinstance(b, _ProtocolMeta) and
                                       b.__origin__ is Protocol
                                       for b in cls.__bases__)
            if cls._is_protocol:
                for base in cls.__mro__[1:]:
                    if not (base in (object, Generic) or
                            base.__module__ == 'collections.abc' and
                            base.__name__ in _PROTO_WHITELIST or
                            isinstance(base, TypingMeta) and base._is_protocol or
                            isinstance(base, GenericMeta) and
                            base.__origin__ is Generic):
                        raise TypeError('Protocols can only inherit from other'
                                        ' protocols, got %r' % base)

                def _no_init(self, *args, **kwargs):
                    if type(self)._is_protocol:
                        raise TypeError('Protocols cannot be instantiated')
                cls.__init__ = _no_init

            def _proto_hook(other):
                if not cls.__dict__.get('_is_protocol', None):
                    return NotImplemented
                if not isinstance(other, type):
                    # Same error as for issubclass(1, int)
                    raise TypeError('issubclass() arg 1 must be a class')
                for attr in _get_protocol_attrs(cls):
                    for base in other.__mro__:
                        if attr in base.__dict__:
                            if base.__dict__[attr] is None:
                                return NotImplemented
                            break
                        annotations = getattr(base, '__annotations__', {})
                        if (isinstance(annotations, typing.Mapping) and
                                attr in annotations and
                                isinstance(other, _ProtocolMeta) and
                                other._is_protocol):
                            break
                    else:
                        return NotImplemented
                return True
            if '__subclasshook__' not in cls.__dict__:
                cls.__subclasshook__ = _proto_hook