我目前想要完成的是调整Pythons itertools
模块函数combinations
,以便在创建组合之前对传递的iterable
进行排序,目标是对返回的组合进行排序。
我是第一次使用Python扩展模块,到目前为止我唯一的经验是编写和编译像Python扩展模块一样的“Hello World”,但我希望我的整个编程经验可以在几个编程中完成。语言是一个足够坚实的基础,我可以在这个挑战上取得成功。
我知道有一个内置的Python函数sorted()
可以对传递给combinations
的迭代进行排序,但我不知道如何从扩展模块的C代码中调用它。
我试过写iterable = sorted(iterable);
,但即使模块编译(带警告),编译模块的导入也会失败ImportError: cgitertools.cpython-36m-x86_64-linux-gnu.so: undefined symbol: sorted
我的问题是:
如何从Python扩展模块的C代码中调用Pythons内置方法(使用示例
sorted()
)?
以下是我尝试过的所有细节及其无效的原因:
combinations_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
combinationsobject *co;
Py_ssize_t n;
Py_ssize_t r;
PyObject *pool = NULL;
PyObject *iterable = NULL;
Py_ssize_t *indices = NULL;
Py_ssize_t i;
static char *kwargs[] = {"iterable", "r", NULL};
if (!PyArg_ParseTupleAndKeywords(args, kwds, "On:combinations", kwargs,
&iterable, &r))
return NULL;
// iterable.sort(); doesn't work ... cgitertoolsmodule.c:2398:13: error: request for member ‘sort’ in something not a structure or union
// iterable.__sort__(); doesn't work either with same error
// COMPILES, but gives ERROR on import in Python:
iterable = sorted(iterable);
$ python3.6 cgitertoolsmodule-setup.py build
running build
running build_ext
building 'cgitertools' extension
gcc -pthread -Wno-unused-result -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/usr/local/include/python3.6m -c cgitertoolsmodule.c -o build/temp.linux-x86_64-3.6/cgitertoolsmodule.o
cgitertoolsmodule.c: In function ‘combinations_new’:
cgitertoolsmodule.c:2400:16: warning: implicit declaration of function ‘sorted’ [-Wimplicit-function-declaration]
iterable = sorted(iterable);
^
cgitertoolsmodule.c:2400:14: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
iterable = sorted(iterable);
^
gcc -pthread -shared build/temp.linux-x86_64-3.6/cgitertoolsmodule.o -o build/lib.linux-x86_64-3.6/cgitertools.cpython-36m-x86_64-linux-gnu.so
$ python3.6
Python 3.6.1 (default, Apr 18 2017, 23:00:41)
[GCC 5.4.1 20160904] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> from cgitertools import combinations
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: cgitertools.cpython-36m-x86_64-linux-gnu.so: undefined symbol: sorted
答案 0 :(得分:1)
你应该从内置函数中获取排序函数,而不是调用它:
PyObject *builtins = PyEval_GetBuiltins();
PyObject *sorted = PyDict_GetItemString(builtins , "sorted");
PyObject *sorted_list = PyEval_CallFunction(sorted, "(O)", iterable);
//... do something with the sorted_list
Py_DECREF(sorted_list);