包装C ++，如何在cython中执行不同的类操作

Question

I am trying to wrap a c++ class with cython , where the class uses another class as input for operator overloading. I don't know how to define the another class type in the python part. I wrote both pxd and pyx file for each class, and imported the Size one into Point. But failed to compile,.I upload the codes here https://github.com/YuboHe/PointSize , Somebody plz give a glimpse and leave me a hint, how to make the operation work, Much appreciation

here are two classes, where Point uses Size as a input for operator overloading

In Point.h

friend Point operator+(const Size& sz,const Point& pnt);  

corresponding pxd file

cdef Point operator+(const Size& sz,const Point& pnt)

In the python definition part, I wrote like this, but it always gives me an error as can not convert object

def __add__(left,right):
        cdef PyPoint pypt
        cdef Point pt
        if isinstance(left,PyPoint):
            if isinstance(right,PyPoint):
                pt = left.cpoint[0] + right.cpoint[0]
                pypt = PyPoint(pt.x,pt.y)
                return pypt
            elif isinstance(right,PySize):
                pt = left.cpoint[0] + right.csize[0] 
                pypt = PyPoint(pt.x,pt.y)
                return pypt

Answer 1

You need to tell Cython that your object is a PyPoint . Do this using a type cast, which is described in the documentation .

if isinstance(left,PyPoint):
    if isinstance(right,PyPoint):
         pt = (<PyPoint>left).cpoint[0] + (<PyPoint>right).cpoint[0]

Alternatively you could skip the isinstance s and do (<PyPoint?>left) , which throws a TypeError if the type isn't right. You'd catch the error and try other options.

Finally you can assign to a typed variable. Again, this throws a TypeError if the types don't match:

cdef PyPoint right_pt
# ...
right_pt = right # catch the error if needed...
right_pt.cpoint[0] # is OK