Cython& C ++：通过引用传递 [英] Cython & C++: passing by reference

问题描述

我是Cython和C ++的noob，所以我有一个关于参数传递的问题。我想避免在以下场景中传递参数的副本：

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) # <-- ??

我想要方法 add_one v 就地。我相信在C ++，你可以通过预先挂起参数& 来实现这一点，这意味着对指针的任何更改都传递给了pointee。这样，你不必担心传递指针或实际对象，即

I want the method 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++

我可以在Cython中做同样的事， def add_one（vector [int] * vect）？

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)?

推荐答案

找到了我自己的问题。显然，你可以通过引用传递，但是函数必须是 cdef 'ed，而不是 def 'ed。即

Found the naswer 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)

这篇关于Cython& C ++：通过引用传递的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！