在以下示例中，P 的 list1 属性表示 A 的实例列表。
class A:
value1: str
class B(A):
value2: str
class P:
list1: List[A]
我想要在变量list1 中保留A 的子类列表（不是A 的实例）。有没有办法在python中做到这一点？
【问题讨论】：
标签： python python-3.x class inheritance types
我尝试从这里的第一个答案复制：How to find all the subclasses of a class given its name?：
class klass():
pass
class popo(klass):
pass
class pepe(klass):
pass
class P():
def get_all_subclasses(self, cls):
subclass_list = []
def recurse(classe):
for subclass in classe.__subclasses__():
subclass_list.append(subclass)
recurse(subclass)
recurse(cls)
return list(set(subclass_list))
a = P()
print(a.get_all_subclasses(klass),'\n')
print(type(a.get_all_subclasses(klass)),'\n')
class papa(klass):
pass
class coco(popo):
pass
print(a.get_all_subclasses(klass),'\n')
输出：
[<class '__main__.popo'>, <class '__main__.pepe'>]
<class 'list'>
[<class '__main__.papa'>, <class '__main__.popo'>, <class '__main__.pepe'>, <class '__main__.coco'>]
或：
class klass:
pass
class popo(klass):
pass
class pepe(klass):
pass
class P:
def __init__(self, classez):
self.list1 = []
self.get_all_subclasses(classez)
pass
def get_all_subclasses(self, cls):
def recurse(classe):
for subclass in classe.__subclasses__():
self.list1.append(subclass)
recurse(subclass) # necessarioo per avere coco nella lista
recurse(cls)
self.list1 = list((self.list1))
return self.list1
a = P(klass)
print(a.list1, "\n")
print(type(a.list1), "\n")
class papa(klass):
pass
class coco(popo):
pass
a = P(klass)
print(a.list1)
我也明白了：
[<class '__main__.popo'>, <class '__main__.pepe'>]
<class 'list'>
[<class '__main__.popo'>, <class '__main__.coco'>, <class '__main__.pepe'>, <class '__main__.papa'>]
使用：
class klass():
pass
class popo(klass):
pass
class pepe(klass):
pass
print(klass.__subclasses__(),'\n')
class papa(klass):
pass
class coco(popo):
pass
print(klass.__subclasses__(),'\n')
我明白了：
[<class '__main__.popo'>, <class '__main__.pepe'>]
[<class '__main__.popo'>, <class '__main__.pepe'>, <class '__main__.papa'>]
【讨论】：
解决方法是使用https://docs.python.org/3/library/typing.html#typing.Type。
from typing import List, Type
class P:
list1: List[Type[A]]
现在，list1 表示从 A 扩展的类列表。
【讨论】：
...
class P:
A.__subclasses__()
>>> [<class '__main__.B'>, <class '__main__.C'>, <class '__main__.D'>]
子类 - 返回对直接继承自该类的类的弱引用列表。 enter link description here
【讨论】：