Python でクラスのすべてのサブクラスを検索するにはどうすればよいですか?

Finding All Subclasses of a Class in Python

To retrieve all classes inherited from a specified base class in Python, utilize the __subclasses__() method. This method is available for new-style classes that extend the object class (the default in Python 3). Here's how it works:

class Foo(object): pass
class Bar(Foo): pass
class Baz(Foo): pass
class Bing(Bar): pass

print([cls.__name__ for cls in Foo.__subclasses__()])
# ['Bar', 'Baz']

print(Foo.__subclasses__())
# [<class '__main__.Bar'>, <class '__main__.Baz'>]

To include subsubclasses, recursion can be used:

def all_subclasses(cls):
    return set(cls.__subclasses__()).union(
        [s for c in cls.__subclasses__() for s in all_subclasses(c)])

print(all_subclasses(Foo))
# {<class '__main__.Bar'>, <class '__main__.Baz'>, <class '__main__.Bing'>}

Note: Subclasses that have not been defined yet (e.g., due to unimported modules) will not be detected by __subclasses__().

Locating Subclasses Using a Class Name String:

When only the class name is available as a string, the following steps are necessary:

1. Find the class using the class name.
2. Utilize __subclasses__() to retrieve the subclasses of the located class.

Finding a Class from a Name String:

The method for locating a class from a name string depends on its expected location:

• If expected within the same module:

  cls = globals()[name]

• If expected within the locals namespace:

  cls = locals()[name]

• If anywhere in the modules:

  import importlib
  modname, _, clsname = name.rpartition('.')
  mod = importlib.import_module(modname)
  cls = getattr(mod, clsname)

Once the class is found, its __subclasses__() method can be used to retrieve the desired list of subclasses.

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