Cython“无法将默认值分配给cdef类，结构或联合中的字段" [英] Cython "Cannot assign default value to fields in cdef classes, structs or unions"

问题描述

我正在尝试将Python代码移植到Cython.我对C的经验非常有限.我正在尝试制作一个相对简单的类，用于存储多维数组.出于这个问题的目的，让我们将其留给属性时间为长度为1的单个一维数组.目前，我收到此错误:

I am making my first attempt at porting Python code to Cython. I only have very limited experience with C. I am trying to make a relatively simple class that stores multidimensional arrays. For the purpose of this question, let's leave it to a single one-dimensional array of length 1 for the attribute time. Currently, I am recieving the error:

    cdef np.ndarray[np.int64_t, ndim=1] time = np.empty([1], dtype=np.int64)
                                       ^
------------------------------------------------------------
data.pyx:22:40: Cannot assign default value to fields in cdef classes, structs or unions

以下是最相关的文件.

data.pyx

import numpy as np
cimport numpy as np


cdef extern from "data_extern.h":

    cppclass _Data "Data":

        np.int64_t time64[1]
        double x_coord, y_coord, z_coord
        _Data(np.int64_t *time, double x, double y, double z)


cdef class Data:

    cdef _Data *thisptr
    cdef np.ndarray[np.int64_t, ndim=1] time = np.empty([1], dtype=np.int64)

    def __cinit__(self, np.int64_t time[1], x, y, z):
        self.thisptr = new _Data(&time[0], x, y, z)

    def __dealloc__(self):
        del self.thisptr

data_extern.h

data_extern.h

#ifndef DATA_EXTERN_H
#define DATA_EXTERN_H

class Data {
    public:
        signed long long time64[1];
        double x_coord, y_coord, z_coord;
        Data();
        Data(signed long long time[1], double x, double y, double z;
        ~Data();
};

#endif

data_extern.cpp

data_extern.cpp

#include <iostream>
#include "data_extern.h"

Data::Data () {}

// Overloaded constructor
Data::Data (signed long long time[1], double x, double y, double z {
    this->time64 = time[0];
    this->x_coord = x;
    this->y_coord = y;
    this->z_coord = z;
}

// Destructor
Data::~Data () {}

我认识到我的代码可能存在多个问题，但是如果有人可以为错误消息提供解释，将不胜感激.

I recognize there could be multiple problems with my code, but if someone could provide an explanation for the error message it would be much appreciated.

推荐答案

问题如错误消息中所述:无法为cdef类的C级属性设置默认值.您可以通过在 __ cinit __ 构造函数中设置值来解决此问题，如下所示:

The problem is as stated in the error message: you cannot set a default value for a cdef class's C-level properties. You can get around this by setting the value in the __cinit__ constructor as follows:

cdef class Data:
    cdef _Data *thisptr
    cdef np.ndarray[np.int64_t, ndim=1] time

    def __cinit__(self, np.int64_t time[1], x, y, z):
        self.thisptr = new _Data(&time[0], x, y, z)
        self.time = np.empty([1], dtype=np.int64)

    def __dealloc__(self):
        del self.thisptr

不过，请注意，整个np.ndarray语法已经过时了.除非您对使用numpy类型感到无所适从(由于与某种C ++库接口，在代码中这似乎是不必要的)，否则可以使用更现代的

As a heads-up though, the whole np.ndarray syntax is rather out of date. Unless you are dead-set on using numpy types (which seem to be unnecessary in your code since you are interfacing with a c++ library of some sort), you can use the more modern typed memoryview syntax. You could import the sized integer types using from libc.stdint cimport * to use those instead of the numpy ones.

这篇关于Cython“无法将默认值分配给cdef类，结构或联合中的字段"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！