我怀疑有一个简单的答案,但我需要一些帮助开始使用Cython.我有一个现有的C代码库,我希望通过Cython向
Python公开.对于我想要公开的每个类,我创建了一个Cython cppclass _ClassName和Python包装类ClassName.
最简单的例子：
Object.h CythonMinimal.pyx setup.py
Object.h的内容：
class Object {
public:
Object clone() {
Object o;
return o;
}
};
CythonMinimal.pyx的内容：
cdef extern from "Object.h":
cdef cppclass _Object "Object":
_Object() except +
_Object clone()
cdef class Object:
cdef _Object *thisptr
def __cinit__(self):
self.thisptr = new _Object()
def __dealloc__(self):
del self.thisptr
def clone(self):
return self.thisptr.clone()
setup.py的内容
from distutils.core import setup
from distutils.extension import Extension
from Cython.Build import cythonize
from Cython.Distutils import build_ext
import os
os.environ["CC"] = "g++-4.7"
os.environ["CXX"] = "g++-4.7"
modules = [Extension("CythonMinimal",["CythonMinimal.pyx"],language = "c++",extra_compile_args=["-std=c++11"],extra_link_args=["-std=c++11"])]
for e in modules:
e.cython_directives = {"embedsignature" : True}
setup(name="CythonMinimal",cmdclass={"build_ext": build_ext},ext_modules=modules)
这是我在编译时得到的错误：
cls ~/workspace/CythonMinimal $python3 setup.py build
running build
running build_ext
cythoning CythonMinimal.pyx to CythonMinimal.cpp
Error compiling Cython file:
------------------------------------------------------------
...
def __dealloc__(self):
del self.thisptr
def clone(self):
return self.thisptr.clone()
^
------------------------------------------------------------
CythonMinimal.pyx:18:27: Cannot convert '_Object' to Python object
building 'CythonMinimal' extension
creating build
creating build/temp.macosx-10.8-x86_64-3.3
g++-4.7 -Wno-unused-result -fno-common -dynamic -DNDEBUG -g -O3 -Wall -Wstrict-prototypes -I/usr/local/include -I/usr/local/opt/sqlite/include -I/usr/local/Cellar/python3/3.3.0/Frameworks/Python.framework/Versions/3.3/include/python3.3m -c CythonMinimal.cpp -o build/temp.macosx-10.8-x86_64-3.3/CythonMinimal.o -std=c++11
cc1plus: warning: command line option '-Wstrict-prototypes' is valid for C/ObjC but not for C++ [enabled by default]
CythonMinimal.cpp:1:2: error: #error Do not use this file,it is the result of a Failed Cython compilation.
error: command 'g++-4.7' Failed with exit status 1
我假设_Object.clone需要返回一个_Object(cppclass类型),但是Objet.clone应该返回一个Object(Python类型).但是怎么样？
解决方法
您正在python函数中返回一个C对象,该对象只允许返回python对象：
def clone(self):
return self.thisptr.clone()
这样做：
cdef _Object clone(self) except *:
return self.thisptr.clone()
但这取决于你想要做什么,你可能想要返回Object而不是_Object,所以我会这样修改它：
cdef class Object:
cdef _Object thisobj
cdef _Object *thisptr
def __cinit__(self,Object obj=None):
if obj:
self.thisobj = obj.thisobj.clone()
self.thisptr = &self.thisobj
def __dealloc__(self):
pass
def clone(self):
return Object(self)
