一个Python Puzzler

Question

如果你对如何在python中执行以下任务有任何建议,我就在徘徊:假设我有以下类:

class A(object): 
    self._classes = []
    def magic(self):
        c.foo() for c in self._classes

class B(object):
    def foo():'''some cool stuff here'''

class C(B):
    def foo():'''very cool stuff'''

class D(B):
    def foo():'''very cool stuff'''

我想要做的是当A类被实例化时,所有类型的B - (C和D)将在self._classes中被实例化,这意味着_classes是[C(),D()].

这样做的一般动机是,我希望用户轻松添加类,而无需了解使用它们的类.任何帮助都会被批评.

Answer 1

瞧(感谢这个答案的all_subclasses()):

# recursively get all subclasses of a given class
def all_subclasses(cls):
    return cls.__subclasses__() + [g for s in cls.__subclasses__()
                                   for g in all_subclasses(s)]

class B(object):
    def foo(self): print '''some cool stuff here in B'''

class C(B):
    def foo(self): print '''very cool stuff in C'''

class D(B):
    def foo(self): print '''very cool stuff in D'''

class E(D):
    def foo(self): print '''very cool stuff in E'''

class A(object):
    def __init__(self):
        self._classes = [cls() for cls in all_subclasses(B)]

    def magic(self):
        for c in self._classes: c.foo()

# usage:
A().magic()

输出:

very cool stuff in C
very cool stuff in D
very cool stuff in E