合并班级成员 [英] Merging Class Members

问题描述

给出这样的类结构：

class A:
    dependencies = ["x", "y"]

class B(A):
    dependencies = ["z"]

class C(A):
    dependencies = ["n", "m"]

class D(C):
    dependencies = ["o"]

我想知道是否有可能编写一个执行以下操作的函数（最好是生活在A类上）：

I want to know if it's possible to write a function (preferably living on class A) that does something along these lines:

@classmethod
def get_all_dependencies(cls):
    return super().get_all_dependencies() + cls.dependencies

对于上述类别，预期输出为：

For the above classes, the expected output would be:

>>> A.get_all_dependencies():
["x", "y"]
>>> B.get_all_dependencies():
["x", "y", "z"]
>>> C.get_all_dependencies():
["x", "y", "n", "m"]
>>> D.get_all_dependencies():
["x", "y", "n", "m", "o"]

显然，上面的代码不起作用-它只返回我调用的类的依赖项。我不确定如何在所有课程上递归使用它？ （我要隐藏 hasattr 检查以确保父类调用 get_all_dependencies（）。）

Obviously the above code doesn't work - it just returns the dependencies of the class I call it on. I'm not sure how to get it to work recursively across all the classes? (I'm eliding a hasattr check to ensure the parent class call get_all_dependencies().)

推荐答案

走 mro 并抓住依赖项是我要做的：

Walk the mro and grab the dependencies is what I'd do:

@classmethod
def get_dep(cls):
    return [d for c in cls.mro()[:-1] for d in getattr(c, 'dependencies')]

其中 cls.mro（）[：-1] 用于排除 object 。

这将返回：

>>> A.get_dep()
['x', 'y']
>>> B.get_dep()
['z', 'x', 'y']
>>> C.get_dep()
['n', 'm', 'x', 'y']
>>> D.get_dep()
['o', 'n', 'm', 'x', 'y']

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