来自 python 字符串的 C 字符数组

Question

我有一个python中的字符串列表，我正在尝试将其传递给C扩展以进行字符分析。到目前为止，我已经将列表分解为单独的字符串 PyObjects。接下来，我希望将这些字符串拆分为单独的字符，以便每个字符串 PyObject 现在都是相应的 C 类型字符数组。不过，我似乎不知道该怎么做。

这是我到目前为止所拥有的：目前在构建 .pyd 文件后，它将返回一个 1 的列表作为 Python 的填充物(所以其他一切都有效(，我只是不知道如何将字符串 PyObject 拆分为 C 类型字符数组。

--- cExt.c ---
#include <Python.h>
#include <stdio.h>
static int *CitemCheck(PyObject *commandString, int commandStringLength) {
// HAALP
//char* commandChars = (char*) malloc(commandStringLength*sizeof(char*));
// char c[] = PyString_AsString("c", commandString);
// printf("%c" , c);
// printf("%s", PyString_AsString(commandString));
// for (int i=0; i<sizeof(commandChars)/sizeof(*commandChars); i++) {
//     printf("%s", PyString_AsString(commandString));
//     printf("%c", commandChars[i]);
// }
return 1; // TODO: RETURN PROPER RESULTANT
}
static PyObject *ClistCheck(PyObject *commandList, int commandListLength) {
PyObject *results = PyList_New(commandListLength);
for (int index = 0; index < commandListLength; index++) {
PyObject *commandString;
commandString = PyList_GetItem(commandList, index);
int commandStringLength = PyObject_Length(commandString);
// CitemCheck should take string PyObject and its length as int
int x = CitemCheck(commandString, commandStringLength);
PyObject* pyItem = Py_BuildValue("i", x);
PyList_SetItem(results, index, pyItem);
}
return results;
}
static PyObject *parseListCheck(PyObject *self, PyObject *args) {
PyObject *commandList;
int commandListLength;
if (!PyArg_ParseTuple(args, "O", &commandList)){
return NULL;
}
commandListLength = PyObject_Length(commandList);
return Py_BuildValue("O", ClistCheck(commandList, commandListLength));
}
static char listCheckDocs[] = 
""; // TODO: ADD DOCSTRING
static PyMethodDef listCheck[] = {
{"listCheck", (PyCFunction) parseListCheck, METH_VARARGS, listCheckDocs},
{NULL,NULL,0,NULL}
};
static struct PyModuleDef DCE = {
PyModuleDef_HEAD_INIT,
"listCheck",
NULL,
-1,
listCheck
};
PyMODINIT_FUNC PyInit_cExt(void){
return PyModule_Create(&DCE);
}

作为参考，我的临时扩展构建文件：

--- _c_setup.py --- 
(located in same folder as cExt.c)
"""
to build C files, pass:
python _c_setup.py build_ext --inplace clean --all
in command prompt which is cd'd to the file's dierctory
"""
import glob
from setuptools import setup, Extension, find_packages
from os import path
here = path.abspath(path.dirname(__file__))
files = [path.split(x)[1] for x in glob.glob(path.join(here, '**.c'))]
extensions = [Extension(
path.splitext(x)[0], [x]
) for x in files]
setup(
ext_modules = extensions,
)

Answer 1

您可以使用PyUnicode_AsEncodedString，它

对 Unicode 对象进行编码，并将结果作为 Python 字节对象返回。 编码和错误与 Unicode encode(( 方法中同名的参数具有相同的含义。要使用的编解码器使用 Python 编解码器注册表进行查找。如果编解码器引发异常，则返回 NULL。

见 https://docs.python.org/3/c-api/unicode.html#c.PyUnicode_AsEncodedString

然后，使用 PyBytes_AsString 您将获得一个指向带有终止 NUL 字节的内部缓冲区的指针。不得释放或修改此缓冲区。如果您需要副本，您可以使用例如strdup。

见 https://docs.python.org/3/c-api/bytes.html#c.PyBytes_AsString

稍微修改一下你的代码，它可能看起来像这样：

PyObject *encodedString = PyUnicode_AsEncodedString(commandString, "UTF-8", "strict");
if (encodedString) { //returns NULL if an exception was raised
char *commandChars = PyBytes_AsString(encodedString); //pointer refers to the internal buffer of encodedString
if(commandChars) {
printf("the string '%s' consists of the following chars:n", commandChars);
for (int i = 0; commandChars[i] != ''; i++) {
printf("%c ", commandChars[i]);
}
printf("n");
}
Py_DECREF(encodedString);
}

如果有人测试：

import cExt
fruits = ["apple", "pears", "cherry", "pear", "blueberry", "strawberry"]         
res = cExt.listCheck(fruits)
print(res)

输出将是：

the string 'apple' consists of the following chars:
a p p l e 
the string 'pears' consists of the following chars:
p e a r s 
the string 'cherry' consists of the following chars:
c h e r r y 
the string 'pear' consists of the following chars:
p e a r 
the string 'blueberry' consists of the following chars:
b l u e b e r r y 
the string 'strawberry' consists of the following chars:
s t r a w b e r r y 
[1, 1, 1, 1, 1, 1]

与问题没有直接关系的旁注： 您的 CitemCheck 函数返回指向 int 的指针，但如果查看它的调用方式，您似乎想要返回一个 int 值。函数签名应如下所示：

static int CitemCheck(PyObject *commandString, int commandStringLength)

(请注意 int 之后删除的*(。