A couple questions about classes and inheritance

[Christian Heimes]

> First, I've looked a fair bit and can't find how one can find the base
> classes of a subclass?  isinstance and issubclass sort of do the
> opposite of what I want.  Surely somewhere there is something like
>
> MyThingee.something.orOther.baseClasses()

You can get the direct parents of a class with the attribute __bases__. 
The class attribute __mro__ returns a tuple of for the method resolution 
order. But instead of poking around yourself I suggest you use the 
inspect module. It provides a high level interface.

>>> class Example:
...     pass
...
>>> Example.__bases__
(<class 'object'>,)
>>> Example.__mro__
(<class '__main__.Example'>, <class 'object'>)


>    But what happens if I try to subclass function?
>
> First attempt:
>>>>
>>>> class MyFunction(function):
> ....       pass
> ....
> Traceback (most recent call last):
>    File "<stdin>", line 1, in<module>
> NameError: name 'function' is not defined

There is no object called function in the list of builtins. You can't 
subclass from function anyway so there is no point in accessing the 
function object. If you want to create some callable class you have to 
provide a method call "__call__". It's called when you call the 
instances of your class like a function.

>>> def a():
...     pass
...
>>> type(a)
<class 'function'>
>>> function = type(a)
>>> class MyFunc(function):
...     pass
...
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
TypeError: type 'function' is not an acceptable base type

> Anyway, again can you point me to somewhere that I can learn more?  In
> particular, is there a list somewhere of the builtin types that are
> not subclassable?

I don't think it's documented anyway. You have to try yourself. In 
general you don't have to subclass builtin types. Some classes are 
tricky to subclass like e.g. immutable classes (str, bytes) or dict.

Christian