在 Python2 中，如何强制 child class 方法调用 parent 方法而不明确要求最终用户包含它？

Question

A parent class 我写的是使用后需要进行一些特定的内部清理。 child class 有自己的清理工作，但 parent 的清理功能必须在运行之后。显然，调用 super 可以解决这个问题，但我希望 child class 方面尽可能简单。

我尝试装饰 parent 方法。这没有用。

# The parent class whose inner-workings I don't expect the end user to understand
class ParentClass(object):
    def __init__(self, *args, **kwargs):
        self._personal_message = "Parent class says:"
        self._important_message = "I'm important!"

    # The method that NEEDS to be run in all instances of ParentClass and its subclasses
    def _important_method(self):
        print(self._important_message)

    # The decorator I thought would work
    def _pretty_decoration(func):
        def func_wrapper(self):
            func_self = func(self)
            self._important_method()
            return func_self
        return func_wrapper

    # The decorated function that will be overridden by the child class
    @_pretty_decoration
    def do_something(self):
        print(self._personal_message)

    # Make the decorator static
    _pretty_decoration = staticmethod(_pretty_decoration)


# The blissfully naive Child class
class ChildClass(ParentClass):
    def __init__(self, *args, **kwargs):
        super(ChildClass, self).__init__(*args, **kwargs)
        self._personal_message = "Child class says:"

    # The overriding method
    def do_something(self):
        print(self._personal_message)
        self.do_something_else()

    def do_something_else(self):
        print("I am blissfully naive.")


# The test drive
parent = ParentClass()
parent.do_something()
child = ChildClass()
child.do_something()

在这个例子中，我得到：

Parent class says:
I'm important!
Child class says:
I am blissfully naive.

而我希望得到：

Parent class says:
I'm important!
Child class says:
I am blissfully naive.
I'm important!

我应该怎么做才能达到预期的效果？

Answer 1

与其覆盖该方法，不如将真正的工作推迟到从 do_something 调用的回调方法。那么就没有理由覆盖do_something，你可以直接将对_important_method的调用放在它的主体中。

class ParentClass(object):
    def __init__(self, *args, **kwargs):
        self._personal_message = "Parent class says:"
        self._important_message = "I'm important!"

    # The method that NEEDS to be run in all instances
    # of ParentClass and its subclasses
    def _important_method(self):
        print(self._important_message)

    # This doesn't get overriden; it's a fixed entry point to do_body
    def do_something(self):
        self.do_body()
        self._important_method()

    # This shouldn't (need to) be called directly
    def do_body(self):
        print(self._personal_message)


class ChildClass(ParentClass):
    def do_body(self):
        print(self._personal_message)  # or super().do_body()
        self.do_something_else()

    def do_something_else(self):
        print("I am blissfully naive.")

那么下面的仍然有效

child = ChildClass()
child.do_something()

在 Python2 中，如何强制 child class 方法调用 parent 方法而不明确要求最终用户包含它？

In Python2, how to force a child class method to call a parent method without explicitly requiring the end user to include it?

python

inheritance

python-2.x