问作为类编写的简单装饰器，它计算一个函数被调用了多少次
EN

Code Review用户

提问于 2019-03-10 04:03:17

回答 1查看 127关注 0票数 2

我能改进它的打字吗？你还会做什么其他的改善或仿生改变吗？

F = TypeVar('F', bound=Callable[..., Any])


# This is mostly so that I practice using a class as a decorator.
class CountCalls:
    """Logs to DEBUG how many times a function gets called, saves the result in a newly created attribute `num_calls`."""
    def __init__(self, func: F) -> None:
        functools.update_wrapper(self, func)
        self.func = func
        self.num_calls: int = 0
        self._logger = logging.getLogger(__name__ + '.' + self.func.__name__)
        self.last_return_value = None

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        self.num_calls += 1
        self._logger.debug(' called %s times', self.num_calls)
        self.last_return_value = self.func(*args, **kwargs)
        return self.last_return_value

下面是装修师的作品：

>>> @CountCalls
... def asdf(var: str):
...     print(var)
...     return len(var)
... 
>>> asdf('Laur')
Laur
4
DEBUG:__main__.asdf: called 1 times
>>> asdf('python 3')
DEBUG:__main__.asdf: called 2 times
python 3
8
>>> asdf(3)
DEBUG:__main__.asdf: called 3 times
3
Traceback (most recent call last):
  File "<input>", line 1, in <module>
  File "C:/Projects/Python/he/src/he/decorators.py", line 156, in __call__
    self.last_return_value = self.func(*args, **kwargs)
  File "<input>", line 4, in asdf
TypeError: object of type 'int' has no len()
>>> asdf.num_calls
3

python

python-3.x

meta-programming

回答 1

Code Review用户

发布于 2019-03-10 08:57:35

您可以尝试改进类型的一件事是键入方法本身(虽然我不确定工具对它的支持程度)。另外，引导/尾随空格应该由记录器来决定，而不是使用它的代码。

F = TypeVar('F', bound=Callable[..., Any])


# This is mostly so that I practice using a class as a decorator.
class CountCalls:
    """Logs to DEBUG how many times a function gets called, saves the result in a newly created attribute `num_calls`."""
    def __init__(self, func: F) -> None:
        functools.update_wrapper(self, func)
        self.func = func
        self.num_calls: int = 0
        self._logger = logging.getLogger(__name__ + '.' + self.func.__name__)
        self.last_return_value = None

    __call__: F

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        self.num_calls += 1
        self._logger.debug(f'called %s times', self.num_calls)
        self.last_return_value = self.func(*args, **kwargs)
        return self.last_return_value

至于代码本身，您可以创建一个基于回调的API。

F = TypeVar('F', bound=Callable[..., Any])


# This is mostly so that I practice using a class as a decorator.
class CountCalls:
    """Logs to DEBUG how many times a function gets called, saves the result in a newly created attribute `num_calls`."""
    def __init__(self, func: F, callback: Optional[Callable[[int, Tuple[Any], Dict[str, Any]], Any]] = None) -> None:
        if callback is None:
            logger = logging.getLogger(__name__ + '.' + self.func.__name__)

            def callback(num_calls: int, args: Tuple[Any], kwargs: Dict[str, Any]):
                self._logger.debug(f'called %s times', self.num_calls)

        functools.update_wrapper(self, func)
        self.func = func        
        self.callback = callback
        self.num_calls: int = 0
        self.last_return_value = None

    __call__: F

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        self.num_calls += 1
        self.callback(self.num_calls, args, kwargs)
        self.last_return_value = self.func(*args, **kwargs)
        return self.last_return_value

或者使用回调中跟踪的呼叫数量(为了提高灵活性)：

F = TypeVar('F', bound=Callable[..., Any])


# This is mostly so that I practice using a class as a decorator.
class CountCalls:
    """Logs to DEBUG how many times a function gets called, saves the result in a newly created attribute `num_calls`."""
    def __init__(self, func: F, callback: Optional[Callable[[int, Tuple[Any], Dict[str, Any]], Any]] = None) -> None:
        if callback is None:
            logger = logging.getLogger(__name__ + '.' + self.func.__name__)
            num_calls: int = 0

            def callback(args: Tuple[Any], kwargs: Dict[str, Any]):
                nonlocal num_calls  # Not sure if this is necessary or not
                num_calls += 1
                self._logger.debug(f'called %s times', self.num_calls)

        functools.update_wrapper(self, func)
        self.func = func        
        self.callback = callback
        self.last_return_value = None

    __call__: F

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        self.callback(self.num_calls, args, kwargs)
        self.last_return_value = self.func(*args, **kwargs)
        return self.last_return_value

更早的时候，为了在使用关键字时传递关键字参数，需要使用@functools.partial(CountCalls, callback=callback)。现在，可以使用@CountCalls(callback=callback)代替。

F = TypeVar('F', bound=Callable[..., Any])


# This is mostly so that I practice using a class as a decorator.
class CountCalls:
    """Logs to DEBUG how many times a function gets called, saves the result in a newly created attribute `num_calls`."""
    def __init__(self, func: F = None, callback: Optional[Callable[[int, Tuple[Any], Dict[str, Any]], Any]] = None) -> None:
        if callback is None:
            logger = logging.getLogger(__name__ + '.' + self.func.__name__)
            num_calls: int = 0

            def callback(args: Tuple[Any], kwargs: Dict[str, Any]):
                nonlocal num_calls  # Not sure if this is necessary or not
                num_calls += 1
                self._logger.debug(f'called %s times', self.num_calls)

        if func is None:
            return functools.partial(CountCalls, callback=callback)

        functools.update_wrapper(self, func)
        self.func = func        
        self.callback = callback
        self.last_return_value = None

    __call__: F

    def __call__(self, *args: Any, **kwargs: Any) -> Any:
        self.callback(self.num_calls, args, kwargs)
        self.last_return_value = self.func(*args, **kwargs)
        return self.last_return_value