Passing C++ pointer as argument into Cython function

Question

cdef extern from \"Foo.h\":
    cdef cppclass Bar:
        pass

cdef class PyClass:
    cdef Bar *bar

    def __cinit__(self, Bar *b)
        bar = b

Answer 1

Python class accepts Python arguments. To pass a C++ argument you need to wrap it:

# distutils: language = c++

cdef extern from "Foo.h" namespace "baz":
    cdef cppclass Bar:
         Bar(double d)
         double get()

cdef class PyBar: # wrap Bar class
    cdef Bar *thisptr
    def __cinit__(self, double d):
        self.thisptr = new Bar(d)
    def __dealloc__(self):
        del self.thisptr
    property d:
        def __get__(self):
            return self.thisptr.get()

PyBar instances can be used as any other Python objects both from Cython and pure Python:

class PyClass:
    def __init__(self, PyBar bar):
        self.bar = bar

print(PyClass(PyBar(1)).bar.d)