Python 2.7 - 使用类作为时间和记忆的装饰器

Question

我是 Python 的新手，我目前正在做一个项目，我有一个 Timer 和 Memoize 类，它们都应该能够用作装饰器，并且可以使用具有任意数量参数的函数.

问题

我目前的问题是我试图将它们都用作函数的装饰器；但是，Timer 仅在第一次调用函数时调用，而不是第二次调用。例如，使用以下代码：

# Import the Memoize class from the memoization module
from memoization import Memoize


# Import the time module
import time


# Import the logging module
import logging


# Import the Timer class from the timer module
from timer import Timer


@Memoize
@Timer
def pass_and_square_time(seconds):
    # Call time.sleep(seconds)
    time.sleep(seconds)
    # Return the square of the input seconds amount.
    return seconds**2


def main():
    logging.getLogger().setLevel(logging.ERROR)

    print '\nFor pass_and_square_time({30}):'.format(n=num)
    print '\n\tThe initial call of pass_and_square_time(30) yields: {ret}'.format(ret=pass_and_square_time(30))
    print '\n\tThe second call of pass_and_square_time(30) yields: {ret}'.format(ret=pass_and_square_time(30))

返回以下内容：

For pass_and_square_time(30):

<function pass_and_square_time at 0x02B9A870> 30.003000021 seconds

    The initial call of pass_and_square_time(30) yields: 900

    The second call of pass_and_square_time(30) yields: 900

当我希望它也返回第二次调用之上的秒数时（因为那是第二次的时间。初始调用之上的时间是初始调用的时间）。我相信@Memoize 装饰器在第二次调用时工作正常，因为它最初在第一次调用之后出现，而不是执行 time.sleep(30) 调用。

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定时器

我的 Timer 类实现如下：

class Timer(object):
    def __init__(self, fcn, timer_name='Timer'):
        self._start_time = None
        self._last_timer_result = None
        self._display = 'seconds'
        self._fcn = fcn
        self._timer_name = timer_name
        self.__wrapped__ = self._fcn

    def __call__(self, *args):
        self.start()
        fcn_res = self._fcn(*args)
        self.end()
        print '\n{func} {time} seconds'.format(func=self._fcn, time=self.last_timer_result)
        return fcn_res

    '''
    start(), end(), and last_timer_result functions/properties implemented 
    below in order to set the start_time, set the end_time and calculate the 
    last_timer_result,  and return the last_timer_result. I can include more
    if you need it. I didn't include it just because I didn't want to make
    the post too long
    '''

---

记忆

我的 Memoize 类实现如下：

class Memoize(object):
    def __init__(self, fcn):
        self._fcn = fcn
        self._memo = {}
    self.__wrapped__ = self.__call__

def __call__(self, *args):
    if args not in self._memo:
        self._memo[args] = self._fcn(*args)

    return self._memo[args]

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使用的参考文献

我查看并尝试模拟我的课程的参考资料是：

Python 类装饰器

• https://krzysztofzuraw.com/blog/2016/python-class-decorators.html
• Using classes as method decorators
• Python decorator best practice, using a class vs a function

Python 记忆

• https://www.python-course.eu/python3_memoization.php

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感谢您的阅读和您能提供的任何帮助！

Answer 1

使用您的代码，您正在记忆一个定时函数，这意味着当在缓存中找到参数时也会跳过定时代​​码。如果你颠倒装饰器的顺序

@Timer
@Memoize
def pass_and_square_time(seconds):
    # Call time.sleep(seconds)
    time.sleep(seconds)
    # Return the square of the input seconds amount.
    return seconds**2

现在你正在计时一个记忆函数。无论参数是否在缓存中找到，您都可以为调用 memoized 函数计时。