Cython & C++: pasando por referencia

I am a noob with Cython and C++, so I have a question on argument passing. I want to avoid passing a copy of an argument in the following scenario:

# somefile.pyx
#distutils: language = c++
from libcpp.vector cimport vector

def add_one(vector[int] vect):
    cdef int i
    n = vect.size()
    for i in range(n):
        vect[i] += 1

cdef vector[int] v
for i in range(100000):
    v.push_back(i)
add_one(v) # <-- ??

quiero el metodo add_one to just modify v "in-place." I believe in C++, you can achieve this by pre-pending the argument with &, which means that any changes to the pointer is passed to the pointee. That way, you don't have to worry about passing a pointer or the actual object, i.e.

add_one(v); # in c++

Can I do the same in Cython, or do I have to explicitly change the arg type to a reference instead, i.e. def add_one(vector[int]* vect)?

preguntado el 12 de febrero de 14 a las 07:02

Somewhat related question on usuarios-cython: "Question about pass-by-reference" -

1 Respuestas

Found the answer to my own question. Apparently, you can pass by reference, but the function MUST be cdef'ed, not def'ed. i.e.

# somefile.pyx
#distutils: language = c++
from libcpp.vector cimport vector

cdef void add_one(vector[int]& vect):
    cdef int i
    n = vect.size()
    for i in range(<int>n):
        vect[i] += 1

cdef vector[int] v
for i in range(100000):
    v.push_back(i)
add_one(v)

Respondido 20 Jul 17, 13:07

i do pass-by-ref for std::string but can't change its value inside the function - Dee

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