[英]C++ Python module import error: “undefined symbol: Py_InitModule3” ( Py_InitModule () )
我剛開始嘗試在C中編寫我的第一個Python擴展模塊,並使用https://www.tutorialspoint.com/python/python_further_extensions.htm中提供的說明。
我在Linux Mint 18.1上,在其virtualenv版本中使用Python 3.6.1。
作為第一步,我編寫了一個非常簡約的Python模塊版本。
這是我的C代碼:
include <Python.h>
static PyObject* uniqueCombinations(PyObject* self)
{
return Py_BuildValue("s", "uniqueCombinations() return value (is of type 'string')");
}
static char uniqueCombinations_docs[] =
"usage: uniqueCombinations(lstSortableItems, comboSize)\n";
static PyMethodDef uniqueCombinations_funcs[] = {
{"uniqueCombinations", (PyCFunction)uniqueCombinations,
METH_NOARGS, uniqueCombinations_docs},
{NULL}
};
void inituniqueCombinations(void)
{
Py_InitModule3("uniqueCombinations", uniqueCombinations_funcs,
"Extension module uniqueCombinations v. 0.01");
}
這里是我用來編譯C代碼到uniqueCombinations.cpython-36m-x86_64-linux-gnu.so
的setup.py文件的代碼:
from distutils.core import setup, Extension
setup(name='uniqueCombinations', version='0.01', \
ext_modules=[Extension('uniqueCombinations', ['uniqueCombinations_pythonCmodule_v-0.01_Cg.c'])])
令我驚訝的是,導入時模塊無法正確加載:
>>> import uniqueCombinations
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: uniqueCombinations.cpython-36m-x86_64-linux-gnu.so: undefined symbol: Py_InitModule3
為什么我收到此錯誤?
我該怎么做才能正確加載已編譯的模塊?
這里的構建協議帶有關於Py_InitModule3的隱式聲明的警告:
$ python uniqueCombinations_pythonCmodule_v-0.01_setup.py_Cg.py build
running build
running build_ext
building 'uniqueCombinations' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/local/include/python3.6m -c uniqueCombinations_pythonCmodule_v-0.01_Cg.c -o build/temp.linux-x86_64-3.6/uniqueCombinations_pythonCmodule_v-0.01_Cg.o
uniqueCombinations_pythonCmodule_v-0.01_Cg.c: In function ‘inituniqueCombinations’:
uniqueCombinations_pythonCmodule_v-0.01_Cg.c:19:5: warning: implicit declaration of function ‘Py_InitModule3’ [-Wimplicit-function-declaration]
Py_InitModule3("uniqueCombinations", uniqueCombinations_funcs,
^
creating build/lib.linux-x86_64-3.6
gcc -pthread -shared build/temp.linux-x86_64-3.6/uniqueCombinations_pythonCmodule_v-0.01_Cg.o -o build/lib.linux-x86_64-3.6/uniqueCombinations.cpython-36m-x86_64-linux-gnu.so
不再使用Py_InitModule(Py_InitModule3)。 有必要改為創建PyModuleDef結構,然后將對它的引用傳遞給PyModule_Create。
在導入時創建的模塊不會引發錯誤的C代碼下面:
#include <Python.h>
static PyObject* uniqueCombinations(PyObject* self)
{
return Py_BuildValue("s", "uniqueCombinations() return value (is of type 'string')");
}
static char uniqueCombinations_docs[] =
"usage: uniqueCombinations(lstSortableItems, comboSize)\n";
/* deprecated:
static PyMethodDef uniqueCombinations_funcs[] = {
{"uniqueCombinations", (PyCFunction)uniqueCombinations,
METH_NOARGS, uniqueCombinations_docs},
{NULL}
};
use instead of the above: */
static PyMethodDef module_methods[] = {
{"uniqueCombinations", (PyCFunction) uniqueCombinations,
METH_NOARGS, uniqueCombinations_docs},
{NULL}
};
/* deprecated :
PyMODINIT_FUNC init_uniqueCombinations(void)
{
Py_InitModule3("uniqueCombinations", uniqueCombinations_funcs,
"Extension module uniqueCombinations v. 0.01");
}
*/
static struct PyModuleDef Combinations =
{
PyModuleDef_HEAD_INIT,
"Combinations", /* name of module */
"usage: Combinations.uniqueCombinations(lstSortableItems, comboSize)\n", /* module documentation, may be NULL */
-1, /* size of per-interpreter state of the module, or -1 if the module keeps state in global variables. */
module_methods
};
PyMODINIT_FUNC PyInit_Combinations(void)
{
return PyModule_Create(&Combinations);
}
這里的構建協議:
$ python uniqueCombinations_pythonCmodule_v-0.01_setup.py_Cg.py build
running build
running build_ext
building 'Combinations' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/local/include/python3.6m -c uniqueCombinations_pythonCmodule_v-0.01_Cg.c -o build/temp.linux-x86_64-3.6/uniqueCombinations_pythonCmodule_v-0.01_Cg.o
gcc -pthread -shared build/temp.linux-x86_64-3.6/uniqueCombinations_pythonCmodule_v-0.01_Cg.o -o build/lib.linux-x86_64-3.6/Combinations.cpython-36m-x86_64-linux-gnu.so
和成功導入的交互式Python控制台會話:
>>> import Combinations
>>> dir(Combinations)
['__doc__', '__file__', '__loader__', '__name__', '__package__', '__spec__', 'uniqueCombinations']
>>> Combinations.__doc__
'usage: Combinations.uniqueCombinations(lstSortableItems, comboSize)\n'
>>> Combinations.uniqueCombinations()
"uniqueCombinations() return value (is of type 'string')"
>>>
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