Python functools.singledispatch() Examples

def convert_yielded(yielded):
    """Convert a yielded object into a `.Future`.

    The default implementation accepts lists, dictionaries, and Futures.

    If the `~functools.singledispatch` library is available, this function
    may be extended to support additional types. For example::

        @convert_yielded.register(asyncio.Future)
        def _(asyncio_future):
            return tornado.platform.asyncio.to_tornado_future(asyncio_future)

    .. versionadded:: 4.1
    """
    # Lists and dicts containing YieldPoints were handled earlier.
    if isinstance(yielded, (list, dict)):
        return multi(yielded)
    elif is_future(yielded):
        return yielded
    elif isawaitable(yielded):
        return _wrap_awaitable(yielded)
    else:
        raise BadYieldError("yielded unknown object %r" % (yielded,)) 

def import_single_dispatch():
    try:
        from functools import singledispatch
    except ImportError:
        singledispatch = None

    if not singledispatch:
        try:
            from singledispatch import singledispatch
        except ImportError:
            pass

    if not singledispatch:
        raise Exception(
            "It seems your python version does not include "
            "functools.singledispatch. Please install the 'singledispatch' "
            "package. More information here: "
            "https://pypi.python.org/pypi/singledispatch"
        )

    return singledispatch


# noqa 

def test_c_classes(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        @g.register(decimal.DecimalException)
        def _(obj):
            return obj.args
        subn = decimal.Subnormal("Exponent < Emin")
        rnd = decimal.Rounded("Number got rounded")
        self.assertEqual(g(subn), ("Exponent < Emin",))
        self.assertEqual(g(rnd), ("Number got rounded",))
        @g.register(decimal.Subnormal)
        def _(obj):
            return "Too small to care."
        self.assertEqual(g(subn), "Too small to care.")
        self.assertEqual(g(rnd), ("Number got rounded",)) 

def convert_yielded(yielded):
    """Convert a yielded object into a `.Future`.

    The default implementation accepts lists, dictionaries, and Futures.

    If the `~functools.singledispatch` library is available, this function
    may be extended to support additional types. For example::

        @convert_yielded.register(asyncio.Future)
        def _(asyncio_future):
            return tornado.platform.asyncio.to_tornado_future(asyncio_future)

    .. versionadded:: 4.1
    """
    # Lists and dicts containing YieldPoints were handled earlier.
    if yielded is None:
        return moment
    elif isinstance(yielded, (list, dict)):
        return multi(yielded)
    elif is_future(yielded):
        return yielded
    elif isawaitable(yielded):
        return _wrap_awaitable(yielded)
    else:
        raise BadYieldError("yielded unknown object %r" % (yielded,)) 

def test_mro(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        class A:
            pass
        class C(A):
            pass
        class B(A):
            pass
        class D(C, B):
            pass
        def g_A(a):
            return "A"
        def g_B(b):
            return "B"
        g.register(A, g_A)
        g.register(B, g_B)
        self.assertEqual(g(A()), "A")
        self.assertEqual(g(B()), "B")
        self.assertEqual(g(C()), "A")
        self.assertEqual(g(D()), "B") 

def test_mro(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        class A:
            pass
        class C(A):
            pass
        class B(A):
            pass
        class D(C, B):
            pass
        def g_A(a):
            return "A"
        def g_B(b):
            return "B"
        g.register(A, g_A)
        g.register(B, g_B)
        self.assertEqual(g(A()), "A")
        self.assertEqual(g(B()), "B")
        self.assertEqual(g(C()), "A")
        self.assertEqual(g(D()), "B") 

def import_single_dispatch():
    try:
        from functools import singledispatch
    except ImportError:
        singledispatch = None

    if not singledispatch:
        try:
            from singledispatch import singledispatch
        except ImportError:
            pass

    if not singledispatch:
        raise Exception(
            "It seems your python version does not include "
            "functools.singledispatch. Please install the 'singledispatch' "
            "package. More information here: "
            "https://pypi.python.org/pypi/singledispatch"
        )

    return singledispatch 

def test_c_classes(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        @g.register(decimal.DecimalException)
        def _(obj):
            return obj.args
        subn = decimal.Subnormal("Exponent < Emin")
        rnd = decimal.Rounded("Number got rounded")
        self.assertEqual(g(subn), ("Exponent < Emin",))
        self.assertEqual(g(rnd), ("Number got rounded",))
        @g.register(decimal.Subnormal)
        def _(obj):
            return "Too small to care."
        self.assertEqual(g(subn), "Too small to care.")
        self.assertEqual(g(rnd), ("Number got rounded",)) 

def test_c_classes(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        @g.register(decimal.DecimalException)
        def _(obj):
            return obj.args
        subn = decimal.Subnormal("Exponent < Emin")
        rnd = decimal.Rounded("Number got rounded")
        self.assertEqual(g(subn), ("Exponent < Emin",))
        self.assertEqual(g(rnd), ("Number got rounded",))
        @g.register(decimal.Subnormal)
        def _(obj):
            return "Too small to care."
        self.assertEqual(g(subn), "Too small to care.")
        self.assertEqual(g(rnd), ("Number got rounded",)) 

def convert_yielded(yielded):
    """Convert a yielded object into a `.Future`.

    The default implementation accepts lists, dictionaries, and Futures.

    If the `~functools.singledispatch` library is available, this function
    may be extended to support additional types. For example::

        @convert_yielded.register(asyncio.Future)
        def _(asyncio_future):
            return tornado.platform.asyncio.to_tornado_future(asyncio_future)

    .. versionadded:: 4.1
    """
    # Lists and dicts containing YieldPoints were handled earlier.
    if isinstance(yielded, (list, dict)):
        return multi(yielded)
    elif is_future(yielded):
        return yielded
    elif isawaitable(yielded):
        return _wrap_awaitable(yielded)
    else:
        raise BadYieldError("yielded unknown object %r" % (yielded,)) 

def test_mro(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        class A:
            pass
        class C(A):
            pass
        class B(A):
            pass
        class D(C, B):
            pass
        def g_A(a):
            return "A"
        def g_B(b):
            return "B"
        g.register(A, g_A)
        g.register(B, g_B)
        self.assertEqual(g(A()), "A")
        self.assertEqual(g(B()), "B")
        self.assertEqual(g(C()), "A")
        self.assertEqual(g(D()), "B") 

def methdispatch(func):
    """
    A decorator that is used to support singledispatch style functionality
    for instance methods. By default, singledispatch selects a function to
    call from registered based on the type of args[0]:

        def wrapper(*args, **kw):
            return dispatch(args[0].__class__)(*args, **kw)

    This uses singledispatch to do achieve this but instead uses args[1]
    since args[0] will always be self.
    """

    dispatcher = singledispatch(func)

    def wrapper(*args, **kw):
        return dispatcher.dispatch(args[1].__class__)(*args, **kw)

    wrapper.register = dispatcher.register
    update_wrapper(wrapper, dispatcher)

    return wrapper 

def test_mro(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        class A:
            pass
        class C(A):
            pass
        class B(A):
            pass
        class D(C, B):
            pass
        def g_A(a):
            return "A"
        def g_B(b):
            return "B"
        g.register(A, g_A)
        g.register(B, g_B)
        self.assertEqual(g(A()), "A")
        self.assertEqual(g(B()), "B")
        self.assertEqual(g(C()), "A")
        self.assertEqual(g(D()), "B") 

def convert_yielded(yielded):
    """Convert a yielded object into a `.Future`.

    The default implementation accepts lists, dictionaries, and Futures.

    If the `~functools.singledispatch` library is available, this function
    may be extended to support additional types. For example::

        @convert_yielded.register(asyncio.Future)
        def _(asyncio_future):
            return tornado.platform.asyncio.to_tornado_future(asyncio_future)

    .. versionadded:: 4.1
    """
    # Lists and dicts containing YieldPoints were handled earlier.
    if isinstance(yielded, (list, dict)):
        return multi(yielded)
    elif is_future(yielded):
        return yielded
    elif isawaitable(yielded):
        return _wrap_awaitable(yielded)
    else:
        raise BadYieldError("yielded unknown object %r" % (yielded,)) 

def applicationpolicy(arg: Callable) -> Callable:
    """
    Decorator for application policy method.

    Allows policy to be built up from methods
    registered for different event classes.
    """

    assert isfunction(arg), arg

    @no_type_check
    def _mutator(func):
        wrapped = singledispatch(func)

        @wraps(wrapped)
        def wrapper(*args, **kwargs):
            event = kwargs.get("event") or args[-1]
            return wrapped.dispatch(type(event))(*args, **kwargs)

        wrapper.register = wrapped.register

        return wrapper

    return _mutator(arg) 

def encoderpolicy(arg=None):
    """
    Decorator for encoder policy.

    Allows default behaviour to be built up from methods
    registered for different types of things, rather than
    chain of isinstance() calls in a long if-else block.
    """

    def _mutator(func):
        wrapped = singledispatch(func)

        @wraps(wrapped)
        def wrapper(*args, **kwargs):
            obj = kwargs.get("obj") or args[-1]
            return wrapped.dispatch(type(obj))(*args, **kwargs)

        wrapper.register = wrapped.register

        return wrapper

    assert isfunction(arg), arg
    return _mutator(arg) 

def encoderpolicy(arg=None):
    """
    Decorator for encoder policy.

    Allows default behaviour to be built up from methods
    registered for different types of things, rather than
    chain of isinstance() calls in a long if-else block.
    """

    def _mutator(func):
        wrapped = singledispatch(func)

        @wraps(wrapped)
        def wrapper(*args, **kwargs):
            obj = kwargs.get("obj") or args[-1]
            return wrapped.dispatch(type(obj))(*args, **kwargs)

        wrapper.register = wrapped.register

        return wrapper

    assert isfunction(arg), arg
    return _mutator(arg) 

def test_c_classes(self):
        @functools.singledispatch
        def g(obj):
            return "base"
        @g.register(decimal.DecimalException)
        def _(obj):
            return obj.args
        subn = decimal.Subnormal("Exponent < Emin")
        rnd = decimal.Rounded("Number got rounded")
        self.assertEqual(g(subn), ("Exponent < Emin",))
        self.assertEqual(g(rnd), ("Number got rounded",))
        @g.register(decimal.Subnormal)
        def _(obj):
            return "Too small to care."
        self.assertEqual(g(subn), "Too small to care.")
        self.assertEqual(g(rnd), ("Number got rounded",)) 

def to_dict(obj, **kwargs):
    """
    Convert an object into dictionary. Uses singledispatch to allow for
    clean extensions for custom class types.

    Reference: https://pypi.python.org/pypi/singledispatch

    :param obj: object instance
    :param kwargs: keyword arguments such as suppress_private_attr,
                   suppress_empty_values, dict_factory
    :return: converted dictionary.
    """

    # if is_related, then iterate attrs.
    if is_model(obj.__class__):
        return related_obj_to_dict(obj, **kwargs)

    # else, return obj directly. register a custom to_dict if you need to!
    #   reference: https://pypi.python.org/pypi/singledispatch
    else:
        return obj 

def convert_yielded(yielded: _Yieldable) -> Future:
    """Convert a yielded object into a `.Future`.

    The default implementation accepts lists, dictionaries, and
    Futures. This has the side effect of starting any coroutines that
    did not start themselves, similar to `asyncio.ensure_future`.

    If the `~functools.singledispatch` library is available, this function
    may be extended to support additional types. For example::

        @convert_yielded.register(asyncio.Future)
        def _(asyncio_future):
            return tornado.platform.asyncio.to_tornado_future(asyncio_future)

    .. versionadded:: 4.1

    """
    if yielded is None or yielded is moment:
        return moment
    elif yielded is _null_future:
        return _null_future
    elif isinstance(yielded, (list, dict)):
        return multi(yielded)  # type: ignore
    elif is_future(yielded):
        return typing.cast(Future, yielded)
    elif isawaitable(yielded):
        return _wrap_awaitable(yielded)  # type: ignore
    else:
        raise BadYieldError("yielded unknown object %r" % (yielded,)) 

def dispatchmethod(
        func: Callable[[Any, TARG],
                       TRET]) -> DispatchMethodWrapper[TARG, TRET]:
    """A variation of functools.singledispatch for methods."""
    from functools import singledispatch, update_wrapper
    origwrapper: Any = singledispatch(func)

    # Pull this out so hopefully origwrapper can die,
    # otherwise we reference origwrapper in our wrapper.
    dispatch = origwrapper.dispatch

    # All we do here is recreate the end of functools.singledispatch
    # where it returns a wrapper except instead of the wrapper using the
    # first arg to the function ours uses the second (to skip 'self').
    # This was made with Python 3.7; we should probably check up on
    # this in later versions in case anything has changed.
    # (or hopefully they'll add this functionality to their version)
    def wrapper(*args: Any, **kw: Any) -> Any:
        if not args or len(args) < 2:
            raise TypeError(f'{funcname} requires at least '
                            '2 positional arguments')

        return dispatch(args[1].__class__)(*args, **kw)

    funcname = getattr(func, '__name__', 'dispatchmethod method')
    wrapper.register = origwrapper.register  # type: ignore
    wrapper.dispatch = dispatch  # type: ignore
    wrapper.registry = origwrapper.registry  # type: ignore
    # pylint: disable=protected-access
    wrapper._clear_cache = origwrapper._clear_cache  # type: ignore
    update_wrapper(wrapper, func)
    # pylint: enable=protected-access
    return cast(DispatchMethodWrapper, wrapper) 

def __init__(self, func):
            if not callable(func) and not hasattr(func, "__get__"):
                raise TypeError("{!r} is not callable or a descriptor".format(func))

            self.dispatcher = singledispatch(func)
            self.func = func 

def singledispatchmethod(func):
        dispatcher = singledispatch(func)

        def wrapper(*args, **kw):
            return dispatcher.dispatch(args[1].__class__)(*args, **kw)

        wrapper.register = dispatcher.register
        update_wrapper(wrapper, func)
        return wrapper 

def symbolic_dispatch(f = None, cls = object):
    if f is None:
        return lambda f: symbolic_dispatch(f, cls)

    # TODO: don't use singledispatch if it has already been done
    dispatch_func = singledispatch(f)

    if cls is not object:
        dispatch_func.register(cls, f)
        dispatch_func.register(object, _dispatch_not_impl(dispatch_func.__name__))


    @dispatch_func.register(Symbolic)
    def _dispatch_symbol(__data, *args, **kwargs):
        return create_sym_call(FuncArg(dispatch_func), strip_symbolic(__data), *args, **kwargs)

    @dispatch_func.register(Call)
    def _dispatch_call(__data, *args, **kwargs):
        # TODO: want to just create call, for now use hack of creating a symbolic
        #       call and getting the source off of it...
        return strip_symbolic(create_sym_call(FuncArg(dispatch_func), __data, *args, **kwargs))

    return dispatch_func

    
# Do some gnarly method setting ----------------------------------------------- 

def dispatch(func):
    dispatcher = singledispatch(func)

    def wrapper(*args, **kw):
        return dispatcher.dispatch(args[1].__class__)(*args, **kw)

    def register(cls, func=None):
        if isinstance(cls, EObject):
            return dispatcher.register(cls.python_class)
        return dispatcher.register(cls)
    wrapper.register = register
    update_wrapper(wrapper, func)
    return wrapper


# def install_issubclass_patch():
#     old_issubclass = builtins.issubclass
#
#     def pyecore_issubclass(self, cls):
#         if isinstance(self, EClass):
#             return old_issubclass(self.python_class, cls)
#         return old_issubclass(self, cls)
#     pyecore_issubclass.original = old_issubclass
#     builtins.issubclass = pyecore_issubclass
#
#
# class original_issubclass(object):
#     def __init__(self):
#         self.pyecore_issubclass = builtins.issubclass
#
#     def __enter__(self):
#         builtins.issubclass = self.pyecore_issubclass.original
#
#     def __exit__(self, type_, value, traceback):
#         builtins.issubclass = self.pyecore_issubclass 

def methdispatch(func):
    dispatcher = singledispatch(func)
    def wrapper(*args, **kw):
        return dispatcher.dispatch(args[1].__class__)(*args, **kw)
    wrapper.register = dispatcher.register
    update_wrapper(wrapper, func)
    return wrapper 

def __init__(self, data_source, config=None, **kwargs):
        self.config = config
        self.data_source = data_source
        self.read_dispatcher = singledispatch(self.read)
        self.read_dispatcher.register(list, self._read_list)
        self.read_dispatcher.register(ClipIdentifier, self._read_clip)
        self.read_dispatcher.register(MultiFramesInputIdentifier, self._read_frames_multi_input)

        self.validate_config()
        self.configure() 

def __init__(self, value_differ, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.value_differ = value_differ
        self.calculate_diff = singledispatch(self._calculate_diff_regression_rep)
        self.calculate_diff.register(DepthEstimationAnnotation, self._calculate_diff_depth_estimation_rep) 

def singledispatch2(cls, f = None):
    """Wrap singledispatch. Making sure to keep its attributes on the wrapper.
    
    This wrapper has three jobs:
        1. strip symbols off of calls
        2. pass NoArgs instance for calls like some_func(), so dispatcher can handle
        3. return a Pipeable when the first arg of a call is a symbol
    """

    # classic way of allowing args to a decorator
    if f is None:
        return lambda f: singledispatch2(cls, f)

    # initially registers func for object, so need to change to pd.DataFrame
    dispatch_func = singledispatch(f)
    if isinstance(cls, tuple):
        for c in cls: dispatch_func.register(c, f)
    else:
        dispatch_func.register(cls, f)
    # then, set the default object dispatcher to create a pipe
    register_pipe(dispatch_func, object)

    # register dispatcher for Call, and NoArgs
    pipe_call(dispatch_func)
    pipe_no_args(dispatch_func)

    @wraps(dispatch_func)
    def wrapper(*args, **kwargs):
        strip_args = map(strip_symbolic, args)
        strip_kwargs = {k: strip_symbolic(v) for k,v in kwargs.items()}

        if not args:
            return dispatch_func(NoArgs(), **strip_kwargs)

        return dispatch_func(*strip_args, **strip_kwargs)

    return wrapper 

def get_mutation_params(info):
        @singledispatch
        def _parse_ast_value(arg, info):  # pragma: no cover
            raise RuntimeError(f"Unknown arg {arg}")

        @_parse_ast_value.register(ast.ObjectValue)
        def _(arg, info):
            return {
                field.name.value: _parse_ast_value(field.value, info)
                for field in arg.fields
            }

        @_parse_ast_value.register(ast.ListValue)
        def _(arg, info):
            return [_parse_ast_value(val, info) for val in arg.values]

        @_parse_ast_value.register(ast.StringValue)
        def _(arg, info):
            return arg.value

        @_parse_ast_value.register(ast.Variable)
        def _(arg, info):
            return info.variable_values[arg.name.value]

        # No need to keep the registered singledispatch implementation
        # in the namespace
        del _

        current_sel = [
            sel
            for sel in info.operation.selection_set.selections
            if sel.name.value == info.field_name
            # if aliases are used, we need to compare them as well
            and (sel.alias is None or sel.alias.value == info.path[0])
        ][0]

        return {
            arg.name.value: _parse_ast_value(arg.value, info)
            for arg in current_sel.arguments
        }