包装获取和设置属性方法而不编辑原始 Class

Question

我正在尝试在属性设置 or/and 之前或之后执行一些操作。这段代码棘手的部分是我不能修改原来的 class.

class 的方法没有问题，它按预期工作。但是我找不到处理属性的方法。我有一个错误：

TypeError: readonly attribute

如果有人可以帮助我找到正确的方向......

这是Class我不能修改的:

class Test(object):
    def __init__(self):
        super(Test, self).__init__()
        self._param = None
        self._controler = None
        self._message = None
    @property
    def param(self):
        return self._param
    @param.setter
    def param(self, param):
        self._param = param

    @property
    def controler(self):
        return self._controler

    def message(self):
        print('message')

这是我为完成这项工作而编写的包装器，它将成为我模块的一部分

def add_things_before_and_after(function_to_enhance):
    def new_wrapper(self):
        print("Before function execution") 
        function_to_enhance(self)
        print("After function execution")
    return new_wrapper

这是为使用包装器和实例化 class

而编写的代码

# this one works as expected
Test.message = add_things_before_and_after(Test.message)
# these two lines does not work
Test.param.fget = add_things_before_and_after(Test.param.fget)
Test.controler.fget = add_things_before_and_after(Test.controler.fget)

test = Test()
test.message()
test.param = 1
print(test.param)
print(test.controler)

Answer 1

这可以通过用新的覆盖整个 param 属性来实现。但是，您的装饰器函数必须固定为 return 包装函数的值。

functools.wraps 是保留包装函数的属性（名称、文档等）的好方法。

from functools import wraps

def add_things_before_and_after(function_to_enhance):
    @wraps(function_to_enhance)
    def new_wrapper(self):
        print("Before function execution")
        r = function_to_enhance(self)
        print("After function execution")
        return r
    return new_wrapper

# this one works as expected
Test.message = add_things_before_and_after(Test.message)

# these two lines should work
Test.param = property(add_things_before_and_after(Test.param.fget), Test.param.fset)
Test.controler = property(add_things_before_and_after(Test.controler.fget), Test.controler.fset)

test = Test()
test.message()
test.param = 1
print(test.param)
print(test.controler)

# ==Output==
#
# Before function execution
# message
# After function execution
# Before function execution
# After function execution
# 1
# Before function execution
# After function execution
# None

包装获取和设置属性方法而不编辑原始 Class

Wrap get and set attributes methods without editing original Class

python

oop

wrapper