input_validation.py 文件源码

def expect_types(*_pos, **named):
    """
    Preprocessing decorator that verifies inputs have expected types.

    Usage
    -----
    >>> @expect_types(x=int, y=str)
    ... def foo(x, y):
    ...    return x, y
    ...
    >>> foo(2, '3')
    (2, '3')
    >>> foo(2.0, '3')
    Traceback (most recent call last):
       ...
    TypeError: foo() expected an argument of type 'int' for argument 'x', but got float instead.  # noqa
    """
    if _pos:
        raise TypeError("expect_types() only takes keyword arguments.")

    for name, type_ in iteritems(named):
        if not isinstance(type_, (type, tuple)):
            raise TypeError(
                "expect_types() expected a type or tuple of types for "
                "argument '{name}', but got {type_} instead.".format(
                    name=name, type_=type_,
                )
            )

    def _expect_type(type_):
        # Slightly different messages for type and tuple of types.
        _template = (
            "%(funcname)s() expected a value of type {type_or_types} "
            "for argument '%(argname)s', but got %(actual)s instead."
        )
        if isinstance(type_, tuple):
            template = _template.format(
                type_or_types=' or '.join(map(_qualified_name, type_))
            )
        else:
            template = _template.format(type_or_types=_qualified_name(type_))

        return make_check(
            TypeError,
            template,
            lambda v: not isinstance(v, type_),
            compose(_qualified_name, type),
        )

    return preprocess(**valmap(_expect_type, named))