Function head_from_fun

celery/utils/functional.py:354–384

Generate signature function from actual function.

(fun: Callable[..., Any], bound: bool = False)

def head_from_fun(fun: Callable[..., Any], bound: bool = False) -> str:
    """Generate signature function from actual function."""
    # we could use inspect.Signature here, but that implementation
    # is very slow since it implements the argument checking
    # in pure-Python.  Instead we use exec to create a new function
    # with an empty body, meaning it has the same performance as
    # as just calling a function.
    is_function = inspect.isfunction(fun)
    is_callable = callable(fun)
    is_cython = fun.__class__.__name__ == 'cython_function_or_method'
    is_method = inspect.ismethod(fun)

    if not is_function and is_callable and not is_method and not is_cython:
        name, fun = fun.__class__.__name__, fun.__call__
    else:
        name = fun.__name__
    definition = FUNHEAD_TEMPLATE.format(
        fun_name=name,
        fun_args=_argsfromspec(_getfullargspec(fun)),
        fun_value=1,
    )
    logger.debug(definition)
    namespace = {'__name__': fun.__module__}
    # pylint: disable=exec-used
    # Tasks are rarely, if ever, created at runtime - exec here is fine.
    exec(definition, namespace)
    result = namespace[name]
    result._source = definition
    if bound:
        return partial(result, object())
    return result


def arity_greater(fun, n):