可自定义属性的装饰器

场景：想写一个装饰器来包装一个函数，并且允许用户提供参数在运行时控制装饰器行为。

from functools import wraps, partial
import logging


def attach_wrapper(obj, func=None):
    """
    如果需要减少某个函数的参数个数，可以使用 functools.partial() 。
    partial() 函数允许给一个或多个参数设置固定的值，减少接下来被调用时的参数个数

    """
    if func is None:
        return partial(attach_wrapper, obj)
    setattr(obj, func.__name__, func)
    return func


def logged(level, name=None):
    """
    Add logging to a function. level is the logging
    level, name is the logger name. If name aren't 
    specified, they default to the function's module and name.
    """

    def decorate(func):
        logging.basicConfig(level=logging.DEBUG, format='%(asctime)s - %(name)s - %(levelname)s - %(message)s')
        log_name = name if name else func.__module__
        log = logging.getLogger(log_name)

        @wraps(func)
        def wrapper(*args, **kwargs):
            result = func(*args, **kwargs)
            log.log(level, result)
            return result

        @attach_wrapper(wrapper)
        def set_level(new_level):
            nonlocal level
            level = new_level

        @attach_wrapper(wrapper)
        def get_level():
            return level

        # wrapper.get_level = lambda: level

        return wrapper

    return decorate


@logged(logging.DEBUG)
def add(x, y):
    return x + y


if __name__ == '__main__':
    add(3, 2)

    add.set_level(logging.INFO)
    add(5, 5)

    print(add.get_level())

2019-02-19 16:29:22,195 - __main__ - DEBUG - 5
2019-02-19 16:29:22,195 - __main__ - INFO - 10
20