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points by sakesun 2 days ago | 0 comments

I've been doing things in Python for over 20 years. Only recently I learn that I can do this.

    >>> Dog.__bases__ = (Cat,)
    >>> isinstance(dog, Dog)
    True
    >>> isinstance(dog, Cat)
    True
    >>>

Smalltalk, Self, Common Lisp, Ruby as well, no big deal in regards to JIT code.

This is wild. Is it part of Python's specification, or an implementation detail of CPython?

As far as I understand, CPython implementation is THE specification. Some billions dollar ERP system firmly rely on this behavior, btw.

Yeah, I was afraid you would say that.

Just check with pypy and Graalpy. Both support this as well.

Is the question whether multiple base classes are part of Python’s spec, or if the ability to assign to `__class__` is part of the spec?