在 mixin 类中声明装饰器方法

Question

我写了一个这样的类：

class AbstractBigHandler(AbstractHandler, ActionTimer):
    def __init__(self, path, data_container):
        
        AbstractHandler.__init__(self)
        ActionTimer.__init__(self, data_container)

    @time_action
    def handle(self, request):
        # Do something

我想给其中的handle()方法计时，所以我想出了一个想法来编写一个mixin类，它会在其中提供一个装饰器类，因为在我看来，它可以很好地分离关注点代码。此外，我希望这个 mixin 类可以被我稍后编写的其他类重用：

class ActionTimer:

    def __init__(self, data_container):
        self.data_container = data_container
        self.class_name = self.__class__.__name__

    def time_action(self, func):
        def wrapper(self, func, *args, **kwargs):
            start_time = datetime.now()
            func_output = func.handle(args, kwargs)
            end_time = datetime.now()

            execution_time = end_time - start_time
            print(self.__class__.__name__, " execution time: ", execution_time)

            self.data_container.add_data(self.class_name, execution_time)

            return func_output

        return wrapper

其中的 data_container 参数只是一个我打算浮动的单例，并在其字典属性中收集数据（通过 .add_data() 方法）。

现在，当我尝试为 AbstractBigHandler 类运行测试时，它在实例化时立即失败，并出现以下错误堆栈：

C:\project\tests>python -m unittest test_abstract_big_handler
Traceback (most recent call last):
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\__main__.py", line 18, in <module>
    main(module=None)
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\main.py", line 100, in __init__
    self.parseArgs(argv)
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\main.py", line 147, in parseArgs
    self.createTests()
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\main.py", line 159, in createTests
    self.module)
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\loader.py", line 220, in loadTestsFromNames
    suites = [self.loadTestsFromName(name, module) for name in names]
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\loader.py", line 220, in <listcomp>
    suites = [self.loadTestsFromName(name, module) for name in names]
  File "C:\Users\***\AppData\Local\Continuum\anaconda3\lib\unittest\loader.py", line 154, in loadTestsFromName
    module = __import__(module_name)
  File "C:\project\tests\test_abstract_big_handler.py", line 5, in <module>
    from project.common.handlers.AbstractBigHandler import AbstractBigHandler
  File "C:\project\common\handlers\AbstractBigHandler.py", line 17, in <module>
    class AbstractBigHandler(AbstractHandler, ActionTimer):
  File "C:\project\common\handlers\AbstractBigHandler.py", line 69, in AbstractBigHandler
    @time_action
NameError: name 'time_action' is not defined

我不确定为什么会发生这种情况 - 因为 ActionTimer 类作为第二个继承类添加到 AbstractBigHandler 类中，它的方法 time_action() 应该（并且当我检查 PDB 时）存在于 AbstractBigHandler 的方法中.

帮助？

Answer 1

因为time_action是装饰器，你不需要在wrapped中再次传递func。由于容器是Singleton，所以可以使用classmethod直接引用。

from datetime import datetime
import random


class AbstractHandler(object):
    pass


class ActionTimer(object):
    data_container = []

    def __init__(self, data_container):
        self.data_container = data_container
        self.class_name = self.__class__.__name__

    @classmethod
    def time_action(cls, func):
        def wrapper(*args, **kwargs):
            start_time = datetime.now()
            func_output = func(*args, **kwargs)
            end_time = datetime.now()
            execution_time = end_time - start_time

            # just some random value to show results (remove)
            execution_time = execution_time.total_seconds() + random.randrange(1, 10, 1)

            print(cls.__name__, " execution time: ", execution_time)

            cls.data_container.append((cls.__name__, execution_time))

            return func_output

        return wrapper


class AbstractBigHandler(AbstractHandler, ActionTimer):
    def __init__(self, path, data_container):
        AbstractHandler.__init__(self)
        ActionTimer.__init__(self, data_container)

    @classmethod
    @ActionTimer.time_action
    def handle(cls, request):
        print(request, "CONTAINER:", cls.data_container)


a = AbstractBigHandler("path", [])
for i in range(5):
    a.handle("some-request-" + str(i))
print("FINAL:", ActionTimer.data_container)

产生以下内容：

some-request-0 CONTAINER: []
ActionTimer  execution time:  9.0
some-request-1 CONTAINER: [('ActionTimer', 9.0)]
ActionTimer  execution time:  6.0
some-request-2 CONTAINER: [('ActionTimer', 9.0), ('ActionTimer', 6.0)]
ActionTimer  execution time:  9.0
some-request-3 CONTAINER: [('ActionTimer', 9.0), ('ActionTimer', 6.0), ('ActionTimer', 9.0)]
ActionTimer  execution time:  3.0
some-request-4 CONTAINER: [('ActionTimer', 9.0), ('ActionTimer', 6.0), ('ActionTimer', 9.0), ('ActionTimer', 3.0)]
ActionTimer  execution time:  5.0
FINAL: [('ActionTimer', 9.0), ('ActionTimer', 6.0), ('ActionTimer', 9.0), ('ActionTimer', 3.0), ('ActionTimer', 5.0)]

Answer 2

不幸的是，继承的命名空间仅在类主体被完全定义后处理。对于像AbstractBigHandler 这样的子类来说，在类定义时引用其父类的属性并不容易。一个更简单的问题示例是：

class A:
    foo = 1

class B(A):         # inherit the foo class attribute
    bar = foo + 1   # but looking it up here fails, with the same NameError you're seeing

要解决此问题，您要么需要显式引用父类（例如，B 中的 A.foo），要么将要从父类继承的值改为全局变量。对于需要在定义子类时应用的装饰器，这通常是最好的方法，而不是在将实例作为 self 传递给方法时。

确实，这是我在您的代码中看到的第二个问题，即您的装饰器有一些混乱的参数（在装饰器本身和内部的包装函数中）。我建议这样的结构：

class ActionTimer:
    def __init__(self, data_container):
        self.data_container = data_container
        self.class_name = self.__class__.__name__

def time_action(func):                     # top-level function, no self arg here
    def wrapper(self, *args, **kwargs):    # no func arg here, but we *do* have a self arg
        start_time = datetime.now()
        func_output = func(self, args, kwargs)   # don't call handle, *we're* handle!
        end_time = datetime.now()

        execution_time = end_time - start_time
        print(self.__class__.__name__, " execution time: ", execution_time)

        self.data_container.add_data(self.class_name, execution_time)

        return func_output

    return wrapper

现在AbstractBigHandler 类将按照您编写的方式工作。