python - Method ignored when subclassing a type defined in a C module -

i subclassing type defined in c module alias attributes , methods script works in different contexts.

how work, have tweak dictionary of class manually ? if don't add reference distanceto in dictionnary, point3d has no attribute named distanceto.

class point3d(app.base.vector):       def __new__(cls, x, y, z):           obj = super(point3d, cls).__new__(cls)           obj.x, obj.y, obj.z = x, y, z           obj.__dict__.update({                'x':property(lambda self: self.x),                'y':property(lambda self: self.y),                'z':property(lambda self: self.z),                'distanceto':lambda self, p: self.distancetopoint(p)})           return obj       def distanceto(self, p): return self.distancetopoint(p) 

i thinking once __new__ had returned instance still populate methods , attributes. can shed light on ?

edit : module import freecad. c base type defined there. vector derived form definition here

edit2 : tried following :

class point3d(app.base.vector):       def __new__(cls, x, y, z):           obj = super(point3d, cls).__new__(cls)           obj.x, obj.y, obj.z = x, y, z           obj.__dict__.update({                'x': x, 'y': y, 'z': z,                'distanceto':lambda self, p: self.distancetopoint(p)})            return obj        def distanceto(self, p): return self.distancetopoint(p) 

and after creating second point, both point3d p returns value of last point p.x, p.y , p.z no matter x,y,z parameters passed @ creation of instance. p.x, p.y, p.z return expected values. seems indicate dictionary shared between instances.

edit 3 : problem solved ! py_tpflags_basetype bit set 0 prevent subclassing explained in answer below.

i don't understand why want add properties dynamically. use:

class point3d(app.base.vector):     def __init__(self, x, y, z):         super().__init__(x, y, z)  # or maybe  super().__init__([x, y, z])      @property     def x(self):         return self[0]  # guessing app.base.vector works list      @property.setter     def x(self, value):         self[0] = value      # y , z likewise.