Function pipe

src/attr/_make.py:3349–3406

A converter that composes multiple converters into one. When called on a value, it runs all wrapped converters, returning the *last* value. Type annotations will be inferred from the wrapped converters', if they have any. converters (~collections.abc.Iterable[typing.C

(*converters)

def pipe(*converters):
    """
    A converter that composes multiple converters into one.

    When called on a value, it runs all wrapped converters, returning the
    *last* value.

    Type annotations will be inferred from the wrapped converters', if they
    have any.

        converters (~collections.abc.Iterable[typing.Callable]):
            Arbitrary number of converters.

    .. versionadded:: 20.1.0
    """

    return_instance = any(isinstance(c, Converter) for c in converters)

    if return_instance:

        def pipe_converter(val, inst, field):
            for c in converters:
                val = (
                    c(val, inst, field) if isinstance(c, Converter) else c(val)
                )

            return val

    else:

        def pipe_converter(val):
            for c in converters:
                val = c(val)

            return val

    if not converters:
        # If the converter list is empty, pipe_converter is the identity.
        A = TypeVar("A")
        pipe_converter.__annotations__.update({"val": A, "return": A})
    else:
        # Get parameter type from first converter.
        t = _AnnotationExtractor(converters[0]).get_first_param_type()
        if t:
            pipe_converter.__annotations__["val"] = t

        last = converters[-1]
        if not PY_3_11_PLUS and isinstance(last, Converter):
            last = last.__call__

        # Get return type from last converter.
        rt = _AnnotationExtractor(last).get_return_type()
        if rt:
            pipe_converter.__annotations__["return"] = rt

    if return_instance:
        return Converter(pipe_converter, takes_self=True, takes_field=True)
    return pipe_converter