Question

I want to store C++ objects in a libcpp.map but I can’t get it working. It even doesn’t work on simple integers if I declare the map in the declarations file.

.pxd file:

from libcpp.map cimport map
cdef class MyClass:
    cdef map[int,int] store


.pyx file:

cdef class MyClass:
    def __cinit__(self):
        self.store = map[int,int]()

Following error:

cdef map[int,int] store
          ^
C++ classes not allowed as members of an extension type,
use a pointer or reference instead

Why is this not working? If I declare it inside a function it’s working fine.

Answer 1

going from the error it seems you need to store a pointer to it and invoke a new version on the heap
so

cdef map[int,int] *store

self.store = new map[int,int]()