[Cython] Equivalent of __new__() in python

[Arnaud Bergeron]

Sorry if this is the wrong list to ask questions like that, I couldn't
find any other list for cython.

I am looking for a way to implement the uniqueness of a class in
Cython.  I have a class say:

cdef class Unique(object):
    cdef val

    def __init__(self, val):
        self.val = val

And I want to have only one instance at a time with a single value of val.

I already know how to do this in python using the __new__() method and
a WeakValueDictionary.  I am looking for a way to do the equivalent in
cython.

And if this requires monkey-patching the tp_new slot of the class,
perhaps some pointers as to what should the replacement method should
at least do in order not to screw the rest of the system.

Arnaud