typeassert.py

def typeassert(*ty_args, **ty_kwargs):
    def decorate(func):
        if not __debug__:
            return func
        sig = signature(func)
        bound_types = sig.bind_partial(*ty_args, **ty_kwargs).arguments

        @wraps(func)
        def wrapper(*args, **kwargs):
            bound_values = sig.bind(*args, **kwargs)
            for name, value in bound_values.arguments.items():
                if name in bound_types:
                    if not isinstance(value, bound_types[name]):
                        raise TypeError(
                            'Argument {} must be {}'.format(
                                name, bound_types[name]))
            return func(*args, **kwargs)
        return wrapper
    return decorate