Yes, metaclass does exactly that. E.g. add
class SageObject(object):
__metaclass__ = SageClass
Possible issues are that there are already some metaclasses used in Sage,
e.g. some of the category stuff relies on it but doesn't convey the
metaclass systematically.
Also, there are various Cython limitations (since you can't monkey-patch
cdef stuff)
On Tuesday, March 3, 2015 at 5:38:35 PM UTC+1, Jeroen Demeyer wrote:
>
> This is more a Python question, but maybe somebody knows a solution.
>
> I want to define some kind of hook on a class E which is called whenever
> another class inherits from E.
>
> So the moment somebody does
>
> class SomeOtherClass(E):
> ...
>
> I want a hook function to be called with SomeOtherClass as argument, in
> order to monkey-patch SomeOtherClass. Is this possible?
>
>
> Note: what I *really* want to do is to fix __cmp__() vs. _cmp_(). Sage
> has the very annoying convention that Python classes should use __cmp__
> but Cython classes should use _cmp_. This means that __richcmp__ needs
> to pull some crazy hacks to determine whether the class is a Python or
> Cython class.
>
> The obvious solution is to change __cmp__ to _cmp_ for every Python
> class inheriting from Element (a lot of effort). The non-efficient
> solution is to check for __cmp__ every time _cmp_ needs to be called.
> The optimal solution would be to somehow automatically monkey-patch
> those classes to define _cmp_ as alias for __cmp__.
>
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