Emanuel Barry added the comment: In Objects/typeobject.c#L2290, the code checks that the (meta?)class is exactly `type` and that there's one argument, then returns `Py_TYPE(x)`. Subclasses of `type` allowing a single argument is a side-effect of not overriding __new__, not a documented feature.
Changing the call from `PyType_CheckExact` to `PyType_Check` makes it work, but I'm assuming there may be something I didn't think of. Or maybe there isn't, but either way, I don't consider that this is worth fixing -- if you want to call your subclass with only one argument, override __new__ and do the logic in there. And if you want the type of an object, use type directly. Also, there may be performance concerns here. `type` is heavily optimized in many places; I thought that `PyType_Check` called Python code, but after checking the macro definitions and testing a bit, it turns out I'm wrong. But if there *is* a negative performance impact, this probably can't go in -- this check runs everytime that type() is called, no matter how many arguments, and including in class creation; that's also probably why `PyType_CheckExact` was chosen to begin with. ---------- _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue27157> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
